Post-Translational Modification of Proteins

Summary

This video explains the concept of post-translational modifications (PTMs) and how they add complexity to the proteome. PTMs, such as methylation, acetylation, glycosylation, and ubiquitination, modify proteins after translation, influencing their structure, stability, localization, and function. These modifications help regulate protein activities, including folding, degradation, and interactions within the cell. The video emphasizes that the proteome is far more diverse than the genome, highlighting how PTMs contribute to protein variation and cellular functions, thus offering greater control over biological processes.

Takeaways

• 😀 Post-translational modifications are changes made to proteins after translation, influencing protein function and diversity.
• 😀 The proteome, which represents all the proteins an organism can produce, is much larger than the genome due to various modifications and splicing of mRNA.
• 😀 Unlike the genome, which consists of a finite number of genes, the proteome's size can greatly exceed that due to the diversity of proteins produced.
• 😀 Post-translational modifications include processes like methylation, acetylation, ubiquitination, and more, each affecting protein function in different ways.
• 😀 Methylation adds hydrophobic groups to proteins, influencing their folding and activity, and is involved in both protein and gene regulation.
• 😀 Acetylation involves adding acetyl groups to proteins, influencing their function, and is a modification that affects 90% of human proteins.
• 😀 Glycosylation adds sugar groups to proteins, impacting their folding, distribution, stability, and function.
• 😀 Lipidation adds lipid groups to proteins, targeting them to membrane-bound organelles like the endoplasmic reticulum or mitochondria.
• 😀 Ubiquitination is a modification that marks proteins for degradation, especially misfolded proteins, ensuring cellular quality control.
• 😀 Phosphorylation, a key modification often controlled by kinases, regulates various cellular processes like the cell cycle, growth, and apoptosis.
• 😀 Proteins can also be cleaved by proteases, activating or specializing them for specific functions, such as pepsinogen being cleaved into pepsin for digestion.

Q & A

What is the central dogma of molecular biology?

The central dogma of molecular biology refers to the process where DNA is transcribed into RNA, which is then translated into protein. This is the foundational flow of genetic information in cells.

What are post-translational modifications?

Post-translational modifications are chemical changes made to proteins after they have been translated. These modifications can influence protein function, stability, localization, and activity.

How does the proteome differ from the genome?

While the genome refers to all the genes an organism can express, the proteome encompasses all the proteins that can be expressed. The proteome is more diverse because proteins can undergo various modifications after translation, leading to multiple protein variants from a single gene.

Why is the proteome larger than the genome?

The proteome is larger because, in addition to alternative splicing of mRNA, proteins can undergo various post-translational modifications. This increases the variety of proteins the body can produce, even though the genome has fewer genes.

What is the role of methylation in protein modification?

Methylation involves adding a methyl group to a protein. This hydrophobic group can influence protein folding by making the protein more hydrophobic, affecting its function, stability, and interaction with other molecules.

What effect does acetylation have on proteins?

Acetylation involves adding an acetyl group to a protein, often at its N-terminal. It is involved in regulating protein function, and about 90% of human proteins undergo acetylation, influencing their stability, activity, and interactions.

How does glycosylation affect proteins?

Glycosylation involves adding sugar molecules (mono or polysaccharides) to a protein. This can alter the protein’s folding, localization, stability, and activity, and it can also serve as a signal to direct the protein to specific cell areas.

What is the purpose of lipidation in protein modification?

Lipidation adds lipid groups to a protein to target it to membrane-bound areas, like the endoplasmic reticulum or mitochondria. This makes the protein more compatible with lipid-rich environments, aiding its localization and function.

What is the role of ubiquitination in protein regulation?

Ubiquitination involves adding a small protein called ubiquitin to a target protein, often signaling that it should be degraded. This process is important for removing misfolded proteins or regulating protein levels.

How does phosphorylation regulate protein function?

Phosphorylation adds phosphate groups to proteins, which can dramatically alter their activity. Kinases and phosphatases are enzymes involved in this modification, and it plays a critical role in processes like cell signaling, the cell cycle, and apoptosis.