Post-translational modification

Tiny parts in your body change.

These parts are called proteins. Tiny machines build them first. Then, the proteins change.

They can add new bits. This is like adding a tool. It helps them do a job. Some bits are like sugar. Other bits are like oil. These changes help the proteins work well. They can even send signals.

This helps your body stay healthy.

Your body is made of tiny machines called proteins.

Ribosomes build these proteins first. But the job is not done yet. Proteins often need to change to work well. We call these changes post-translational modifications.

These changes happen after the protein is made. There are more than 650 known types of these changes. Some changes can be undone. Others are permanent.

One way to change is by adding small parts. A protein might get a phosphate group. This is called phosphorylation. It is a very common way to control how a protein works. Proteins can also have sugars added to them. This is called glycosylation. This helps the protein stay stable.

Another way is to add lipids, which are oily parts. This is called lipidation. It helps the protein stick to the cell membrane. Proteins can also be cut into smaller pieces. This helps them become the right shape. For example, insulin is cut to become active. These changes help proteins send signals and do many jobs.

Your body is built from tiny machines called proteins.

These machines are made by small structures called ribosomes. The ribosomes follow instructions to build a chain of amino acids. However, the job is often not finished once the chain is built. Proteins must undergo changes to become fully active and useful. Scientists call these changes post-translational modifications, or PTMs for short.

These changes allow proteins to do many different jobs. There are more than 650 known types of these modifications. They help control how much active protein is available in a cell.

There are many ways a protein can change. One common way is by adding a small group called a phosphate. This specific change is called phosphorylation. It is a very effective way to control how an enzyme works. Another way is called glycosylation, where the cell adds sugar molecules to the protein. This helps the protein fold into the right shape and stay stable.

Some proteins also get oily parts called lipids attached to them. This is called lipidation. This process often helps the protein stick to the cell membrane. These steps act like switches to turn the protein on or off.

Sometimes, a protein is changed by being cut into pieces. This is called proteolytic cleavage. A protein might start as a long, inactive chain called a propeptide. To become a working hormone, it must be cut to its mature form.

For example, the hormone insulin is a great example of this. It is first formed with a middle section that must be removed. The protein is also cut twice after special bonds called disulfide bonds form. This leaves two smaller chains connected together. These precise cuts allow the protein to perform its vital work.

These changes can happen in many different places on a protein. They can occur on the side chains of the amino acids. They can also happen at the very ends of the protein chain. Some changes are caused by helpful enzymes inside the cell. Other changes can happen spontaneously without any help at all. Some changes even happen because of oxidative stress, which is a type of cell damage.

These modifications are very important for signaling and gene expression. If these processes do not work right, it can lead to diseases like cancer.

Learning about these tiny changes helps us understand how life works. You can think of a protein like a piece of clay. The ribosome shapes the basic clay into a long strip. Then, PTMs act like a sculptor's tools to add detail. They might add a tiny bead of sugar or cut the clay into a specific shape.

This turns a simple strip into a complex, working machine. Scientists use special tools like mass spectrometry to see these changes. By studying them, we learn how every living thing stays healthy and organized.

Proteins are the essential molecular machines of life. They are built by ribosomes, which translate mRNA into long polypeptide chains. However, the initial chain is often not a finished product. To become fully functional, proteins must undergo post-translational modifications, or PTMs. These are covalent processes that change a protein after it is synthesized and released from the ribosome. PTMs allow a cell to diversify its protein functions. They extend the capabilities of a protein beyond what is dictated by its genetic transcription. As of 2023, scientists have identified more than 650 known types of PTMs.

These modifications act as a sophisticated regulatory system. They allow the cell to control the levels of active protein available. This process is known as post-translational regulation. While many PTMs are reversible editing events, some are irreversible. One such irreversible event is proteolysis, which is the degradation of a protein. PTMs can occur in both eukaryotic cells and prokaryotic cells. They are vital components in cell signaling. For instance, prohormones must be converted into active hormones through these processes to function correctly.

There are several distinct ways a protein can be modified. One common method is phosphorylation. This involves adding a phosphate group to the protein. Phosphorylation is highly effective for controlling enzyme activity. It is the most common change that occurs after translation. Another major type is glycosylation. This is the attachment of carbohydrate molecules to a protein. Glycosylation can promote proper protein folding and improve stability. It also serves various regulatory functions. Some proteins undergo lipidation, which is the attachment of lipid molecules. This modification often targets a protein to the cell membrane.

Modifications can occur at specific locations on a protein. They often happen on the amino acid side chains. They can also occur at the N-terminus or the C-terminus of the protein. The specific sites chosen for modification often contain functional groups that act as nucleophiles. For example, the hydroxyl groups of serine, threonine, and tyrosine are common sites. The amine forms of lysine, arginine, and histidine are also important. Cysteine provides a thiolate anion for reactions. Aspartate and glutamate provide carboxylates. Even the amide of asparagine can serve as an attachment point for glycans.

Structural changes to the protein backbone are also a form of PTM. Proteolytic cleavage involves cutting peptide bonds. This can process a propeptide into its mature, active form. It can also remove an initiator methionine residue. Another structural change is the formation of disulfide bonds. These bonds form between cysteine residues. The peptide hormone insulin provides a clear example of this complex process. First, disulfide bonds are formed within the chain. Then, the protein is cut twice. This removes a propeptide from the middle of the chain. The final insulin protein consists of two polypeptide chains held together by those disulfide bonds.

Some modifications are not controlled by enzymes. These are known as non-enzymatic modifications. They can occur spontaneously within a living cell. For example, oxidative stress can cause carbonylation. Carbonylation targets a modified protein for degradation. This can lead to the formation of protein aggregates. Specific amino acid modifications can even serve as biomarkers for oxidative damage. Other non-enzymatic processes include glycation, which is the addition of a sugar molecule without an enzyme. In a laboratory setting, scientists use non-enzymatic additions like biotinylation to label proteins for study.

PTMs play a crucial role in regulating cellular processes like signal transduction and gene expression. They work closely with metal ions to influence how cells function. When these interactions become dysregulated, it can lead to serious diseases. These include cancer and various neurodegenerative disorders. To study these complex changes, scientists use advanced experimental techniques. They use mass spectrometry to identify the exact mass of modified proteins. They also use Western blotting and Eastern blotting to detect specific modifications. Understanding these tiny chemical changes helps us understand the very foundation of biological health.