Proteins Translation 4c'
Summary
TLDRThis lecture delves into the intricacies of translation and the genetic code, focusing on the three stages of translation: initiation, elongation, and termination. It distinguishes between prokaryotic and eukaryotic initiation, highlighting the role of the Shine-Dalgarno sequence in prokaryotes and the scanning model in eukaryotes. The lecture also covers the essential components of the translation machinery, such as ribosomes, tRNAs, and various initiation and elongation factors. It further explains the process of peptide bond formation and the role of release factors in terminating translation. Additionally, it touches on the impact of antibiotics that target bacterial translation without affecting eukaryotic cells.
Takeaways
- π¬ Translation is a three-step process: initiation, elongation, and termination, which is crucial for protein synthesis.
- π In prokaryotes, translation initiation involves the Shine-Dalgarno sequence, which helps the small ribosomal subunit bind to the mRNA at the correct site.
- π The initiator tRNA carries a modified methionine (N-formyl-methionine) in prokaryotes, which is the first amino acid added during translation.
- 𧬠Eukaryotic initiation differs as it lacks the Shine-Dalgarno sequence and instead uses a scanning mechanism to find the start codon, often the first AUG.
- π Both prokaryotic and eukaryotic translation initiations require initiation factors and GTP for energy.
- π Elongation is a cyclic process involving tRNA binding, peptide bond formation, and translocation, which is facilitated by elongation factors and GTP.
- π Termination occurs when a ribosome encounters a stop codon, and release factors help in detaching the completed polypeptide chain from the tRNA.
- π± Eukaryotes have a single release factor, eRF, compared to multiple release factors in prokaryotes, highlighting a key difference in the termination process.
- π Translation can occur in the cytoplasm or on the endoplasmic reticulum, influenced by signal peptides that direct the ribosome and mRNA to the ER for proteins destined for secretion or organelles.
- π Antibiotics often target the differences in translation mechanisms between prokaryotes and eukaryotes, inhibiting bacterial protein synthesis without affecting human cells.
Q & A
What are the three steps of translation?
-The three steps of translation are initiation, elongation, and termination.
What is the role of the Shine-Dalgarno sequence in translation initiation?
-The Shine-Dalgarno sequence is a purine-rich sequence upstream from the AUG initiation codon in procaryotes that helps align the mRNA and small ribosomal subunit at the correct location for translation initiation.
How does the initiation of translation differ between procaryotes and eukaryotes?
-In procaryotes, translation initiation involves the Shine-Dalgarno sequence and binding directly to the ribosomal binding site. In eukaryotes, initiation involves binding of the 40S subunit to the 5' cap of the mRNA with the help of eukaryotic initiation factors, followed by scanning for the first AUG codon.
What is the function of the initiator tRNA?
-The initiator tRNA carries the first amino acid, methionine (or its modified form, formylmethionine in procaryotes), to the ribosome during translation initiation.
What is the role of GTP in translation initiation?
-GTP provides the energy required for the binding of the small ribosomal subunit to the mRNA and for the association and dissociation of initiation factors during the initiation process.
How does elongation factor Tu (EF-Tu) contribute to translation elongation?
-Elongation factor Tu (EF-Tu) in procaryotes helps deliver aminoacyl-tRNAs to the ribosome by facilitating their binding to the A site of the ribosome.
What is the significance of the peptidyl transferase center in translation?
-The peptidyl transferase center, which is part of the 23S rRNA in the large ribosomal subunit, catalyzes the formation of peptide bonds between amino acids during translation elongation.
How does translocation occur during translation elongation?
-Translocation is facilitated by elongation factors (EF-G in procaryotes and EF2 in eukaryotes) and GTP, which move the ribosome one codon along the mRNA, shifting the peptidyl-tRNA from the A site to the P site and the empty tRNA from the P site to the E site.
What are the termination codons, and how does translation termination occur?
-The termination codons are UAA, UAG, and UGA, which do not code for any amino acids. During translation termination, release factors bind to these codons in the A site, stimulating peptidyl transferase to cleave the bond between the polypeptide chain and the tRNA, releasing the completed protein.
How can multiple ribosomes translate a single mRNA molecule simultaneously?
-Multiple ribosomes can bind to a single mRNA molecule and translate it simultaneously, forming a polyribosome (or polysome) complex, where each ribosome is translating a different section of the mRNA into a polypeptide chain.
How do antibiotics target bacterial translation without affecting eukaryotic translation?
-Antibiotics target specific components or processes of bacterial translation that differ from those in eukaryotes, such as binding to the 30S ribosomal subunit in bacteria, which has a different structure than the 40S subunit in eukaryotes, thus inhibiting bacterial protein synthesis without affecting eukaryotic cells.
Outlines
π¬ Translation Initiation in Prokaryotes
This paragraph delves into the process of translation initiation in prokaryotes, highlighting the role of the Shine-Dalgarno sequence in mRNA. This purine-rich sequence, located upstream of the AUG initiation codon, is crucial for the correct positioning of the mRNA and small ribosomal subunit. The paragraph explains how the complementary nature of the Shine-Dalgarno sequence to the 16S rRNA in the small subunit facilitates the binding and alignment of the ribosome at the ribosome binding site. The importance of this sequence is underscored by research that involved sequencing and mutating this region to observe effects on translation initiation. The paragraph also introduces the concept of initiation factors and GTP's role in this process.
π Initiation and Methionine's Role in Translation
The paragraph explains that all protein sequences begin with methionine, which is often removed later during protein processing. In prokaryotes, the initiator tRNA carries a modified methionine called N-formylmethionine, which is distinct due to a formaldehyde group added by a transformylase. This modification protects the growing polypeptide chain within the cell. The paragraph describes the formation of the 30S complex, which includes the mRNA, small ribosomal subunit, initiator tRNA, and initiation factors. It also details the subsequent binding of the 50S subunit to form the 70S initiation complex, setting up the ribosome with two binding sites: the A site for incoming aminoacyl tRNAs and the P site for the growing polypeptide chain. The paragraph transitions into discussing the differences in translation initiation between prokaryotes and eukaryotes, noting the absence of a Shine-Dalgarno sequence in eukaryotes and the use of a scanning mechanism instead.
𧬠Eukaryotic Translation Initiation and Elongation
This section contrasts eukaryotic translation initiation with that of prokaryotes, emphasizing the absence of a Shine-Dalgarno sequence and the reliance on a 5' cap and eukaryotic initiation factors, particularly eIF4E, which includes a cap-binding protein. The 40S subunit slides down the mRNA until it encounters the first AUG codon, often initiating translation there. The paragraph also covers the scanning model of translation initiation, introduced by Marilyn Kozak, and the loose consensus sequence surrounding the initiation codon. It transitions into the elongation phase of translation, detailing the three steps: aminoacyl tRNA binding to the A site, peptide bond formation catalyzed by peptidyl transferase (a ribozyme activity of the 23S rRNA), and translocation facilitated by elongation factors and GTP, which move the ribosome and tRNAs to the next codon.
π Elongation and Termination of Translation
The paragraph focuses on the elongation phase of translation, illustrating how the ribosome cycles through binding, peptide bond formation, and translocation until a termination codon is reached. It describes the process of peptide bond formation between the amino acid in the A site and the growing polypeptide chain on the tRNA in the P site, facilitated by peptidyl transferase. The subsequent translocation phase, involving elongation factors and GTP, moves the ribosome and tRNAs to prepare for the next aminoacyl tRNA. The paragraph concludes with a discussion of translation termination, where release factors bind to the stop codon in the A site, stimulating peptidyl transferase to cleave the bond between the tRNA and the polypeptide chain, releasing the completed protein. It also mentions the concept of polysomes, where multiple ribosomes translate a single mRNA molecule simultaneously.
π Antibiotics and Translation Inhibition
The final paragraph discusses the spatial aspects of translation, noting that it can occur in the cytoplasm or be attached to the endoplasmic reticulum, with proteins being translated and translocated into the ER lumen. It touches on post-translational modifications such as phosphorylation and the role of chaperone proteins in protein folding. The paragraph emphasizes how the information encoded in the mRNA sequence not only determines the amino acid sequence of a protein but also contains signals for protein sorting and localization. It concludes by highlighting the medical significance of the differences between prokaryotic and eukaryotic translation, explaining how antibiotics can target bacterial translation without affecting eukaryotic cells, thus serving as a therapeutic strategy.
Mindmap
Keywords
π‘Translation
π‘Genetic Code
π‘Initiation
π‘Shine-Dalgarno Sequence
π‘Elongation
π‘Termination
π‘Ribosome
π‘Anticodon
π‘Methionine
π‘Eukaryotes
π‘Polysome
Highlights
Translation involves three steps: initiation, elongation, and termination.
In prokaryotes, translation initiation involves the Shine-Dalgarno sequence upstream from the AUG start codon.
The Shine-Dalgarno sequence helps the small ribosomal subunit bind to the mRNA at the correct site.
Initiation factors and GTP are crucial for the initiation process in both prokaryotes and eukaryotes.
Eukaryotic translation initiation differs by lacking a Shine-Dalgarno sequence and instead uses a 5' cap and scanning mechanism.
The initiator tRNA carries a modified methionine called N-formylmethionine in prokaryotes.
In eukaryotes, the initiator methionine tRNA is not modified with a formyl group.
Translation elongation consists of three steps: tRNA binding, peptide bond formation, and translocation.
Elongation factors Tu and Ts facilitate aminoacyl-tRNA binding in prokaryotes.
Peptide bond formation is catalyzed by peptidyl transferase, an activity of the 23S rRNA.
Elongation factor G (EF-G) in prokaryotes and EF2 in eukaryotes assist in translocation.
Translation termination occurs when a ribosome encounters a stop codon and release factors are involved.
In prokaryotes, release factors RF1 and RF2 bind to stop codons, while eukaryotes use a single release factor.
Multiple ribosomes can translate a single mRNA molecule simultaneously, forming a polyribosome or polysome.
Translation can occur in the cytoplasm or be attached to the endoplasmic reticulum for proteins destined for secretion.
Antibiotics often target bacterial translation machinery, exploiting differences between prokaryotic and eukaryotic systems.
Transcripts
all right welcome back again this is the
third lecture in the lecture sets on
translation and the genetic code all
right so we ended talking about the
three different steps of translation
initiation elongation and termination
and we talked very briefly about the um
what initiation involves getting that
mRNA and small ribosomal subunit
together um bringing in the initiation
TRNA and then finally bringing in that
large subunit um of the ribosome
together so we'll start by talking about
U translation initiation in procaryotes
and then we'll talk about um initiation
in ukar before moving on to elongation
so procaryotes contain a puring rich
sequence that is about four to seven
nucleotides long Upstream from the AUG
initiation codon and this sequence is
called the shine Del garno sequence okay
so this is going to answer the question
how do the MRNA and small ribosomal
subunit come together at the right place
all right so the shine Del garal
sequence then is in the MRNA it's
Upstream of where translation is going
to start and again translation is going
to start at that Aug codon okay the
start codon so what this looks like is
here so here is the MRNA five Prime to
three prime there's the star codon so
that's going to be the first codon used
to insert the first meth um amino acid
so Upstream to the left here there's
this sequence that's complimentary to
the sequence in the 16srrna so remember
the 16srna is in the small ribosomal
subunit in Pro carots so I mentioned
when you're talking about ribosomes and
the spbg units 16s and stuff I S of
mentioned that it's involved in this
before realize we hadn't quite got there
yet well here we are um and this
sequence then is complimentary so that
helps line up so you remember the 16s
RNA is within the small subunit it helps
line up the small subunit in the right
place along the MRNA so the sequence is
complimentary to the three or sorry the
shin Del sequence is complimentary to
the thre Prime end of this 16sr RNA in
the small ribosomal subunit this
complimentarity then allows a small
ribosomal subunit to bind the MRNA and
what is referred to as a ribosome
binding site so you have the shog garal
sequence and this whole thing where it
sits down and binds is called the
ribosome binding site and this is a site
where the ribosome becomes oriented in
the reading frame for the initiation of
protein synthesis okay so it just gets
it to the right spot so it can start at
the right spot so identifying the
ribosomal binding site and identifying
its necessary role and initiation for
translation was determined in two ways
so how do they know this was important
well they did a couple different things
first they took a bunch of mrnas and
they sequenced this region Upstream of
the star codon okay and what essentially
they're doing they're looking for a
consensus sequence and so they did this
did this they noticed that this sequence
okay or sequence very similar to it was
found in lots of mRNA so it looked
important how do you know for sure it's
important well what they did is they
mutated these sequences to see if
initiation of translation could still
proceed all right so they started making
mutations in here and notice that then
you couldn't start translation properly
then they made complimentary mutation so
they made a mutation here so let's say
they changes G these two G's to use and
you can't get binding and you don't get
translation but if you these are two U's
and then you change these two C's to A's
suddenly you return the complimentarity
and you return the function of being
able to start in the right place so just
a few lines of how research questions
are asked um and really asking whether
nucleotide sequences are important or
not a good way to do that is to mutate
them and see if they can't do what they
normally do and the other way is to try
and return the function by um if you
think complimentarity is important by
mutating um the other strand of RNA or
DNA that's interacting with
it all right so in addition to this
small ribosomal subunit binding
initiation also involves an initiator
TRNA okay three different initiation
factors all right so I don't have that
on this slide initiation Factor 1 2 and
three and GTP for energy so I'm going to
explain as we go through where the
initiation factors sort of come in and
leave and or GP GTP does but I'm not
going to ask you to remember
that specifically know they're involved
okay but I want you to know the other
details and not worry so much but just
know there are initiation factors in GTP
um
involved so initiation Factor one and
initiation factor three and the GTP
molecule are bound to the small
ribosomal subun subunit as it finds and
binds its ribosomal binding site so we
just explain how the small subunit with
the shin doal sequence binds to the
ribosomal binding site and you have an
ation factors in GTP involved Aug okay
again that codon encodes methionine thus
all protein sequences originally begin
with methionine which in many cases is
later removed during protein processing
so even though methionine is always the
first one during translation we'll learn
later and you might have learned in
other classes that proteins get
processed and lots time that involved
cleaving off part of the polypeptide
chain often times and Terminus um but
we're just talking about translation now
and methines always first the first
methionine that is inserted is inserted
by a special TRNA called the initiator
TRNA initiator TRNA carries
methine in procaryotes the initiator
methionine is modified by the addition
of a formal group added by a transformal
a and it's called formal methionine okay
so we have formal methionine so not only
does it have methionine but it has this
formal group covalently attached to the
methionine which makes it slightly
different than any other methionine that
would get um inserted during po during
synthesis of the protein this formal
group on the methionine then blocks the
aminal group of methine from reacting so
it protects the protein while it's being
made um within the cell so at this point
the MRNA 30s subunit formal methionine
TRNA initiation Factor 1 two is known as
the 30s complex okay so this 30s complex
so when all this stuff right above where
it says 30X complex is put together it's
called the 30X complex the 50s subunit
then binds to the 30s complex GTP is
hydrolized and released with initiation
Factor 1 and two and this is then the
70s initiation complex or the entire
initiation complex this complex now has
two binding sites the a site or amino
ail site which will bind any incoming
Amino ACL trnas and the peptidal or P
site which binds the TRNA possess
possessing the growing polypeptide chain
what's unique is at this point
protein synthesis starts with the
initiator methine TRNA in the P site and
so I'll take a look at that here all
right so here's the small ribosomal
subunit you get that they'll show you
just this small portion in pink here of
the 16s RNA that contains the sequence
that binds the shinal sequence so it'll
come in and there's initiation factors
um bind to the shinal sequence that will
Orient the smaller R subunit in the
right spot then the initiator TRNA
methionine will come in here and then
the large ribosomal binding sorry the
large ribosomal subunit will come in and
you can see here that when it's all put
together this initiator TRNA is in the
psite so this is the only point at which
you have a single amino acid on a TRNA
in the psite every time after this
you'll have a growing polypeptide chain
in this P site but this is how
initiation begins
all right so translation initiation in
UK carots is similar to procaryotes with
some differences of course one there is
no shog Garo sequence or equivalent
sequence the 40s subunit when it binds
to the MRNA it binds to the five Prime
cap with the help of a eukariotic
initiation Factor this eukariotic
initiation factor is e
if4 e so not F but 4E so eukariotic
initiation factor for E okay and this
initiation Factor actually consists of
multiple proteins including something
called the CBP that stands for cap
binding protein okay so the 40s subunit
is able to bind to the MRNA with the
help of initiation factor that contains
a cap binding protein this 4ds subunit
then migrates or slides down the five
Prime untranslated region within the
MRNA until it meets the first
Aug and then stops I should say most
often the first Aug is where it stops
this is actually or what this is called
is called the scanning model of
translation initiation all right and
this this model was first put forth by
Marilyn kak the initiation codon is
found within a loose consensus sequence
called the KAC KAC sequence after
Marilyn kak the first Aug is usually
always the initiation Aug okay okay
again biology so they're going to be
exceptions but most of the time you have
this loose consensus sequence within
that is the um a gene so I think I have
here yep so just comparing the two
different ways for RI ribosome RBS
ribosome binding sites shine Del garno
is for procaryotes UK carots you have
this KAC sequence and so here's the
loose consensus for the KAC sequence and
here then is the
initiator um codon within that sequence
all right so the difference is is um in
procaryotes it binds to the site and in
the right orientation here the small
subunit will bind upstream and sort of
scan until it binds more tightly in the
correct orientation um here all right so
here's a pretty complicated slide but um
just look at this part here here's the
MRNA so here's a complex so purple is
the small rabal subunit so you're going
to get initiation factors that are going
to help it again the cap binding protein
bind to the cap and it's going to scan
right until it gets to the right spot so
this is as far as we are right now right
in the middle here um and so the next
step then is the um initiator methionine
on the TRNA entering into the scene so
they show it very early here um so
eukariotic UK carots also have an
initiator methionine but is not modified
does does have a formal group added to
it like a procaryotic one does so in uh
ukar it's also believed that polya
binding protein pabp here also plays a
role in binding one of the initiation
factors at the five Fram cap so here's
initiation Factor 4E with cap binding
protein here it's thought that this poly
binding protein so you can see the MRA
sort of bends around here also helps
with this initiation
event so here's um just slide sort of
comparing bacterial factors initiation
factors elongation factors and release
factors so you got bacterial ones and
their counterparts in your carots and
again I'm not expect you to know all the
names of these things or exactly where
they're acting but but I do want you
know that that there are initiation
factors helping with that event there
are elongation factors helping with the
elongation and you'll see very
specifically how release factors are
involved in termination of translation
all right so to finish up um initiation
and UK carots again binding here getting
to the correct site this initiator TRNA
is in its location here bound to the 40s
subunit and then you get the 60s subunit
coming in and joining so you have the
initiation complex here all right the
complete initiation complex and again
just like in procaryotes in the P site
so you see p site here and the P site
will be where the initiator TRNA with
methine on it is
all right so that was initiation now
we'll move on to translation elongation
so elongation takes place in three steps
or three steps that we can talk about um
first is aminal ACL TRNA binds to the
asite so remember at initiation the
initiator TRNA is in the psite so the
first step is an amino ACL TNA entering
the asite um a peptide bond then forms
and finally the third step is
translocation transfer from the a to the
P site or moving from one site to the
next so you open up a new asite for the
next Amo isolated TRNA to enter so Amo
ACL TRNA binding to the asite is through
the anti-codon codon binding Okay so
we've talked about that so in
procaryotes this binding is facilitated
by GTP and elongation factors so there's
two different elongation factors in
procaryotes you have uh Tu which stands
for temperature unstable and there's
also elongation Factor TS um for temp
temperature stable so just historical
names and how they were named so when
youl TNA elongation Factor Tu complex
comes into the asite and then the eftu
can be uh released um the amino ACL TRNA
associate with elongation or yes
elongation Factor Tu to form a tary
complex which moves into the as site the
ribosome changes shape and then allows
eftu to be released the amuno ACL ends
of the 2 TRNA is those within the A and
P sites are now right next to each other
so the next step then is peptide bond
formation peptidal transferase catalyzes
the peptide bond formation between the
amino acid and the asite and the pite
immediately after the amino ACL TR
binding is complete this pepal
transferase activity is due in part to
the
23srrna
this means that this RNA is acting as an
enzy so it is known as a ribozyme now
both amino acids are linked to the TRNA
in the a
site so this TRNA in the a site is
therefore converted from an amino ACL
TRNA to a peptidal TRNA so last step
then is translocation after the
formation of the peptide bond a peptidal
TRNA is in the a site and an uncharged
TRNA is in the P site elongation factors
EF elongation factors EFG in procaryotes
ef2 in ukar and GTP play roles in this
translocation step EFG appears to fit
into the asite moving the new peptidal
TRNA into the psite and then releasing
the uncharged TRNA is released through
the eite and the ribosome advances to
the next codon placing the pepal TRNA in
the P site this process is repeated
until a termination codon is
reached all right so that was a bunch of
words U makes a little bit easier to
look at it so here's the initiation
complex um actually this shows it
already um three amino acids in but so
here's a peptidal TRNA sitting in the
pite so the next TRNA is going to come
into the a site and again elongation
Factor Tu help it comes in the next step
is peptidal transferase okay and what's
going to happen is
the peptide or growing polypeptide is
going to transfer from the TRNA and the
pite over to the TRNA and the asite it's
going to move from left to right here
which means that that first that green
that first amino acid methine will
always be on the end which it should be
so once that happens then you're going
to get
translocation okay so ribosome's going
to move which is going to push this
deated TRNA into the E site so it can
leave and it's going to move the TRNA
with the growing polypeptide chain into
the P site um the uncharged TRNA will
leave and now you're all set up again
just like you were up here except you
have one more long amino acid opened up
the amino ACL site for the next TRNA to
come in uh similar thing here so TRNA
growing polypeptide chain next one comes
into the a site pepal transferase
growing polypeptide moves from P to a
here get
translocation deated moves out you have
the new TRNA with the growing
polypeptide chain in the correct site so
this shows a little bit more detail
about that peptide bond we've already
looked at what the peptide bond forms
between but so here you have um just a
single
um amino acid here and the amino acid
and the asite peptide bond formation uh
catalyzed by pepal transferase and so it
shows here how this one moves so these
two groups here carboxy group and amino
group are going to join and so this
group here is still on that
end all right protein synthesis
terminates when a ribosome encounters
one of the termination codons also known
as nonsense codons at the close of one
of their elongation Cycles the
Terminator codon lies in the empty a
site after
translocation and so as you know there's
no
TRNA that um recognizes the codon for
the Stop codons so any of those
termination codons there's not a TRNA
that recognizes that all right so in
procaryotes a release Factor RF Factor
binds to the nonsense codon in the as
site there's a couple of different
release factors bind the two of the
different stop
codons release factor three is then a
termination stimulatory Factor so the
release factors stimulate pepal
transferase to cleave the coent bond
between the TRNA and the polypeptide
chain so let me take a look at what that
looks like so here we
have P site with the TR with growing
polypeptide chain stop codon is in the a
site you're going to get a release
factor is going to come in release
Factor 3 is going to help and it's going
to stimulate the TRNA to release the
growing polypeptide chain or you
simulate pepal transferase so basically
it's going to make pepal transferase
cleave this like it's going to join to
another amino acid except of course
there's no another amino acid here and
so it releases the polypeptide once it
release polypeptide that's released from
the ribosome the deated TRNA is release
and then what ends up happening is all
the parts um come apart at that stage so
in ukar termination occurs much the same
way UK carots just have a single release
Factor called e for ukar RF release
Factor one of the few cases I know of
where UK carots have less of something
than procaryotes too so it turns out
then that multiple ribosomes can bind a
single mRNA and translate all at the
same time and there's a term given for
this it's called a poly ribosome or
actually for short it's often called a
polysome so polysome is the complex of
mRNA and the ribosomes that are
simultaneously translating it and again
multiple ribosomes can bind and
translate protein on the same
mRNA and so here's a cting drawing of it
mRNA get multiple ribosomes on here
creating ever longer polypeptides here's
an electron micrograph of that actual
thing so the middle here this line is
the MRNA all these globular structures
are the ribosomes and all these things
little chain like things coming off are
growing polypeptides on that U growing
polypeptides that are being translated
so that's the sort of simplest
explanations of uh translation of course
translation can take place in a couple
different places when the in cell um you
can have it out in cytoplasm or attached
to the um er membrane and I have a
figure here showing that so you can have
out here in the cytoplasm where it just
happens or um sometimes when the
ribosome is undergoing translation of an
mRNA there'll be a particular signal
here called the signal peptide which is
recognized and that then can bring this
uh translating ribosome and mRNA to the
endoplasmic reticulum which then sort of
cycles that growing polypeptide or
translocates it through the membrane
into the Lumen where it can continue to
be made and then it can end up inside
the Lumen of the endoplasmic reticulum
rather than outside in the cytoplasm um
there of course other post- transational
modifications you take something like
cell biology you talk more extensively
about these sorts of things U there's
protein sorting during translation
there's signal sequences that send
protein certain places here's just one
example of a signal sequence sending the
protein to the Lumen of the er um
proteins get help with their folding
with other proteins called chaperonins
that help them do this lots of proteins
get phosphorilated there's a whole group
of proteins called kinases um that add
phosphate groups to different proteins
which either activate or deactivate
those proteins it's a way to regulate it
phosphatases do the exact opposite they
um remove phosphate groups from proteins
um and again the proteins get move from
one place to the other based on a
sequence of amino acids so you it's
interesting you have right a information
within the DNA that codes for the MRNA
that codes for the amino acid and
there's information within that
information um the order of the amino
acids that are made send its own
information as to where the protein
should go whether it should be sorted in
the ER or there's something called the
nuclear localization signal telling it
okay you made this protein here it's got
this signal on it we're supposed to ship
you back in the nucleus because that's
where your where your job
is um so just comparison bacterial nucar
translation so a good summary um of
what's uh what between bacterial and um
eukaryotic so you sort of compare some
of the differences that we've talked
about
here and um oh the other thing last
thing I to mention here is that um a lot
of antibiotics work by actually
specifically targeting or inhibiting
translation in bacterial cells so that
it inhibits bacterial cell translation
but doesn't inhibit translation in
eukariotic cells so those subtle tiny
differences between procaryotes and UK
carots can actually be taken advantage
of in a medical way okay there's
antibiotics that will stop bacterial
cells from being able to translate and
therefore kill the cells but will not
have any uh impact on our cells on
eukariotic cells uh so with that we'll
end this um series of lectures on
translation and genetic code
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