Post-Translational Modification - Online Tutor, Practice Problems & Exam Prep

Post-translational modifications (PTMs) are crucial covalent alterations that regulate protein activity after translation. Key types include methylation (addition of a methyl group), acetylation (addition of an acetyl group), ubiquitination (addition of ubiquitin), and phosphorylation (addition of a phosphate group). Other modifications like hydroxylation, lipidation, and glycosylation also play significant roles. Understanding these modifications is essential for grasping protein functionality and cellular processes, as they influence protein interactions, stability, and activity.

Post-Translational Modification

In this video, we're going to begin our lesson on post translational modifications. And so first, we need to recall from our previous lesson videos that translation is the cellular process of building proteins by using the encoded messages of messenger RNA or mRNA. Now, after translation has been completed and the polypeptide chain has been formed, sometimes post translational modifications will take place, and post translational modifications are sometimes abbreviated as PTMs. Now, post translational modifications or PTMs are covalent alterations that control the protein's activity after translation has been completed. And so there are many different types of post translational modifications and we're going to show you a bunch of post translational modifications down below in our image. But some of the more common types of post translational modifications that you should definitely familiarize yourself with are the 4 that we have listed down below right here, which are methylation, acetylation, ubiquitination, and phosphorylation. So let's take a look down below at our image to get a better understanding of post translational modifications. And so up here at the top what we're showing you is our messenger RNA. And of course, we know that the messenger RNA is going to undergo translation to form our polypeptide chain, our protein whose structure we're showing you right here. Now after translation has been completed, this protein, this polypeptide chain can be modified covalently after translation. And that is why it's called post translational modifications because post means after translation. And so you can see a bunch of different post translational modifications that we have listed here. We're showing you 9 different post translational modifications. But you don't need to memorize, you should familiarize yourself with. But the one you should familiarize yourself with. But the ones that we recommend are here across the top. So here we're showing you hydroxylation which is the addition of a hydroxyl group. Number 2, what we're showing you is methylation. And methylation is going to be the addition of a methyl group, a CH₃ group to the protein, modifying it covalently. Lipidation is going to be the process of adding a lipid to the protein. Acetylation, here, is going to be the process of adding an acetyl group, which you can see here, to the protein. Then disulfide bonds are another type of post translational modification that can link, covalently, 2 separate proteins or can also occur between the same protein disulfide bonds. Ubiquitination is going to be adding a ubiquitin group to the protein, which is a small, ubiquitin is a small protein itself that's going to be added to the protein. Sulfonation is going to be adding a sulfur group, which is represented here as the S to the protein. Glycosylation is going to be adding a carbohydrate to the protein. And then phosphorylation, the last one up here, is going to be adding a phosphate group to the protein after translation. And so once again, there are a bunch of different post translational modifications. There are a lot more than the ones that we've listed here. And so the ones that you are going to need to know are is going to depend on your specific professor. But the ones that we recommend that you should definitely be more familiar with are methylation, acetylation, ubiquitination, and phosphorylation. And so this here concludes our brief introduction to post translational modification. And we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.

Glycosylation is the post-translational addition of ________ to the protein.

• A. A carbohydrate.
• B. A lipid.
• C. A fat.
• D. A nucleotide.

Which of the following is a reversible form of post-translational modification which can activate or deactivate a protein depending on the protein which is being modified?

• A. Glycosylation.
• B. Ubiquitination.
• C. Acetylation.
• D. Phosphorylation.

Here’s what students ask on this topic:

What are post-translational modifications (PTMs) and why are they important?

Post-translational modifications (PTMs) are covalent alterations that occur to proteins after they have been synthesized through translation. These modifications are crucial because they regulate protein activity, stability, interactions, and localization within the cell. PTMs can influence how proteins function and interact with other cellular components, thereby playing a significant role in various cellular processes. Common types of PTMs include methylation, acetylation, ubiquitination, and phosphorylation. Understanding PTMs is essential for comprehending how proteins achieve their final functional forms and how they contribute to cellular physiology and pathology.

What is the difference between methylation and acetylation in post-translational modifications?

Methylation and acetylation are both types of post-translational modifications, but they involve the addition of different chemical groups to proteins. Methylation is the addition of a methyl group (CH₃) to amino acids in a protein, often affecting gene expression and protein interactions. Acetylation, on the other hand, involves the addition of an acetyl group (COCH₃) to lysine residues in proteins, which can influence protein stability, localization, and interactions. Both modifications play critical roles in regulating protein function and cellular processes.

How does ubiquitination affect protein function?

Ubiquitination is a post-translational modification where a ubiquitin protein is covalently attached to a target protein. This process often tags the protein for degradation by the proteasome, a protein complex responsible for breaking down unneeded or damaged proteins. Ubiquitination can also regulate protein activity, localization, and interactions. By controlling protein degradation and function, ubiquitination plays a vital role in maintaining cellular homeostasis and regulating various cellular processes, including cell cycle, DNA repair, and signal transduction.

What role does phosphorylation play in post-translational modifications?

Phosphorylation is a post-translational modification that involves the addition of a phosphate group (PO₄^3-) to specific amino acids, such as serine, threonine, or tyrosine, in a protein. This modification is catalyzed by enzymes called kinases. Phosphorylation can alter a protein's function, activity, interactions, and localization. It is a reversible process, with phosphatases removing the phosphate group. Phosphorylation is crucial for regulating various cellular processes, including signal transduction, cell cycle progression, and metabolic pathways.

What are some common types of post-translational modifications?

Common types of post-translational modifications (PTMs) include methylation (addition of a methyl group), acetylation (addition of an acetyl group), ubiquitination (addition of ubiquitin), and phosphorylation (addition of a phosphate group). Other significant PTMs include hydroxylation (addition of a hydroxyl group), lipidation (addition of a lipid), glycosylation (addition of a carbohydrate), and sulfonation (addition of a sulfur group). These modifications regulate protein activity, stability, interactions, and localization, playing essential roles in various cellular processes.