Post Translational Modifications

Summary

The video script delves into the complexity of the human proteome, highlighting that it contains over a million proteins,远超 the 20,000 to 25,000 genes in the human genome. It explains how mechanisms like alternative splicing and post-translational modifications (PTMs) contribute to this complexity. PTMs, such as phosphorylation and acetylation, are crucial for protein function, affecting activity, localization, and interactions. The script also illustrates how specific modifications, like the removal of methionine in collagen and the acetylation of microtubules, impact protein activity and cellular processes, emphasizing the importance of understanding these modifications for studying diseases.

Takeaways

• 🧬 The human proteome is significantly more complex than the genome, with over 1 million proteins compared to 20,000-25,000 genes.
• 🔑 Single genes can encode multiple proteins through mechanisms like alternative splicing and post-translational modifications (PTMs).
• 🔄 PTMs are crucial for regulating protein function, including activity, localization, and interactions with other cellular molecules.
• 🔬 Two main types of protein modifications are co-translational, occurring while the protein is still attached to the ribosome, and post-translational, occurring after the protein is released.
• ✂️ Collagen is an example of a protein that undergoes post-translational modification, where the initial methionine is removed by proteases.
• 📈 Signal sequences are removed from proteins like insulin to activate them and allow them to perform their functions.
• 🔗 Covalent modifications such as phosphorylation, acetylation, and methylation can alter protein structure and function.
• 🥛 Casein in milk is an example of a protein that undergoes phosphorylation, which helps it bind calcium for bone strength.
• 🧵 Microtubule acetylation is crucial for maintaining their structure during cell division and preventing breakage.
• 🧬 Histone protein methylation regulates gene transcription by either activating or inhibiting the process.
• 🩸 Post-translational modifications are reversible and play a critical role in the study of human diseases and cellular activity regulation.

Q & A

What is the estimated number of proteins in the human proteome?

The estimated number of proteins in the human proteome is over 1 million.

How does the complexity of the human proteome compare to the human genome?

The human proteome is vastly more complex than the human genome, with the genome comprising between 20,000 and 25,000 genes, while the proteome has over 1 million proteins.

What are the mechanisms that generate different mRNA transcripts from a single gene?

The mechanisms that generate different mRNA transcripts from a single gene include genomic recombination, transcription initiation at alternative promoters, differential transcription, termination, and alternative splicing of the transcript.

What is the role of protein post-translational modifications (PTMs) in the proteome?

Protein post-translational modifications (PTMs) play a key role in functional proteomics by regulating activity, localization, and interaction with other cellular molecules such as proteins, nucleic acids, lipids, and cofactors.

What is the difference between co-translational and post-translational modifications?

Co-translational modifications occur while amino acids are still attached to the ribosome, whereas post-translational modifications occur after the protein is no longer attached to the ribosome.

Why is the removal of the initial methionine from a protein important in some cases?

The removal of the initial methionine from a protein like collagen is important because it allows the protein to undergo further processing to form an active, functional protein.

What is the significance of the trimming of signal sequences in protein function?

The trimming of signal sequences is significant because it allows a newly synthesized protein to become active and perform its function after being localized to its destination.

Can you provide an example of a covalent modification and its effect on protein function?

Phosphorylation of serine amino acids in casein helps the protein bind calcium ions, which is crucial for bone strength.

How do disulfide bonds in Immunoglobulin G (IgG) contribute to its function?

Interconnected disulfide bonds in IgG help maintain its shape, which is essential for its function in protecting against bacteria or viral infections.

What is the purpose of carboxylation in pro-thrombin?

Carboxylation of the glutamate residue at the end terminal of pro-thrombin allows binding of calcium ions, which is necessary to initiate blood clotting.

How do post-translational modifications contribute to the study of human diseases?

Post-translational modifications are crucial for studying human diseases because they regulate cellular activity and can be reversible, affecting protein function and biological processes.