Name: protein regulation by covalent bonds
Uploaded: 2023-04-30T18:28:43.000Z
Duration: 2 min 4 s
Channel: JoVE

K12 Standards

Next Generation Science Standards

High School

Life Science

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms: Structures and Processes

HS-LS1-1

Covalently Linked Protein Regulators

Many proteins are regulated by covalently linked molecules, including functional groups, such as methyl or acetyl moieties, and small proteins, such as ubiquitin.
Covalent linkages occur on specific amino acids in the polypeptide chain. For example, phosphate groups are covalently linked to serine, threonine, or tyrosine; methyl and acetyl groups are linked to lysine; and ubiquitin is linked to lysine, cysteine, serine, or threonine residues.
An enzyme or pair of enzymes reversibly catalyzes these post-translational modifications.&#160; An acetyltransferase can acetylate a protein, while a deacetylase can later remove the group.
These modifications can alter a protein&#8217;s function or localization in a cell.
For example, acetylation of histone proteins regulates gene expression by opening up the DNA structure to activate gene transcription. Methylation of histone proteins, on the other hand, is known to repress transcription by tightening the structure.&#160;
Another example is p53, a multidomain tumor suppressor protein that undergoes several covalent modifications in response to stress. Exposure to DNA damaging agents, such as UV and gamma radiation, can result in phosphorylation of the protein.&#160;
Phosphorylation improves stability and activates p53, causing it to bind to DNA damaged by the radiation and prevents cells with mutated DNA from dividing uncontrollably.
In addition to phosphorylation, different types of modifications occurring on a single protein molecule, such as p53, allow it to precisely control its functions such as cell cycle arrest, DNA repair, and apoptosis of a cell.

covalently linked protein regulators

Proteins can undergo many types of post-translational modifications, often in response to changes in their environment. These modifications play an important role in the function and stability of these proteins. Covalently linked molecules include functional groups, such as methyl, acetyl, and phosphate groups, and also small proteins, such as ubiquitin. There are around 200 different types of covalent regulators that have been identified.
These groups modify specific amino acids in a protein. Phosphate groups can only be covalently attached to the amino acids serine, threonine, and tyrosine, whereas methyl and acetyl groups can only be linked to lysine.&#160; These groups are added to and removed from a protein by an enzyme or pair of enzymes.&#160;&#160;&#160; For example, an acetyltransferase adds an acetyl group to a protein, and a deacetylase can remove it. Each of these modifiers can have different effects on the protein to which it is attached depending on the number and location of the modifications. When a single ubiquitin molecule is covalently linked to a certain cell surface receptor, this protein is targeted for endocytosis; on the other hand, when multiple ubiquitins linked together are attached to this protein, it is marked as a target for proteolytic degradation.
A single protein can undergo multiple modifications simultaneously to control its function. One well-known example of a protein regulated by multiple covalent modifications is the tumor-suppressor protein, p53.&#160; p53 undergoes a variety of modifications in response to various types of stress, including radiation and carcinogens. Some modifications include phosphorylation, acetylation, and sumoylation in response to UV and gamma radiations. The sites and types of modifications can vary depending on the stressor. Studies have shown that UV and gamma radiation can result in the phosphorylation of serine 33, but serine 392 can be phosphorylated when exposed to UV but not gamma radiation. Other kinds of stress, such as exposure to hypoxia, anti&#8208;metabolites, and actinomycin D, can result in the acetylation of p53. The modifications can also vary between different cell types and organisms.

Proteins can undergo many types of post-translational modifications, often in response to changes in their environment. These modifications play an ...

Education

JoVE Core

Cell Biology

Unit 1

Protein Function

KEY TERMS AND CONCEPTS

protein regulation by covalent bonds

Protein regulation by covalent bonds helps control how cells respond to changing conditions. A covalent bond is a strong chemical link, and in this context it can change how a protein behaves.

Some regulators work by attaching a chemical group directly to a protein. This covalent change can alter the protein's activity, its location in the cell, or how long it stays active. Because the change is built into the protein itself, it can have a strong effect on cell function.

Covalently linked protein regulators are an important part of cell control and signaling. They help cells turn protein functions on or off at the right time. This type of regulation is a key idea in molecular biology and protein function.

Protein Regulation by Covalent Bonds

ligand binding sites

Ligand Binding Sites in Proteins

Ligand binding sites are specific parts of a protein where a ligand can attach. A ligand is a molecule that binds to another molecule, often to help start or change a biological process. These sites matter because the shape and chemistry of the protein help determine which ligands can fit and bind. Proteins do not bind every ligand in the same way. The binding site provides a matching surface that supports a close interaction. In many cases, this interaction is important for how cells respond...

protein-protein interfaces

Protein Binding Surfaces and Contacts

Protein binding surfaces and contacts help proteins recognize and attach to each other. These interfaces are the regions where two proteins meet and interact. They are important for many cell processes and for how proteins work together. A protein-protein interface is not just a random touch point. It is shaped by the three-dimensional form of each protein. The matching surfaces allow a stable interaction to form when the proteins fit together well. Studying these interfaces helps explain how...

conserved binding sites

Conserved Binding Sites in Protein Families

Conserved binding sites are regions on proteins that stay similar across related proteins. These shared areas often help proteins interact with the same molecules. For this reason, they are useful clues when comparing protein families. A conserved site can help identify where a protein binds. It can also show which parts of the protein are important for function. When the same pattern appears in several proteins, it suggests that the site has been kept through evolution. Scientists look at...

cofactors and coenzymes

Enzyme Helpers: Metals and Vitamins

Enzyme helpers include cofactors and coenzymes. Enzymes are proteins made of amino acids, and the functional groups on those amino acids can drive many chemical reactions through ionic interactions or acid-base reactions. But amino acids alone cannot handle oxidation-reduction and group transfer reactions, so they need non-protein helpers called cofactors. Cofactors are often described as the chemical teeth of an enzyme. They can be metal ions or organic molecules called coenzymes. These...

cooperative allosteric transitions

Allosteric Changes in Protein Shape

Allosteric changes in protein shape help explain how some proteins switch between active and inactive states. These transitions are cooperative, which means a change in one part of the protein can affect other parts of the same molecule. The video focuses on how these shifts in shape support protein function. It also shows that allosteric transitions can be described with different models. In the concerted model, the protein changes shape as a whole. In the sequential model, the change happens...

protein kinases and phosphatases

Protein Kinases and Phosphatases in Cell Control

Protein kinases and phosphatases help control how proteins work in cells. Kinases add phosphate groups to proteins. Phosphatases remove those phosphate groups. This phosphorylation and dephosphorylation process can change a protein’s shape and activity. It is one way cells turn protein function on or off at the right time. These changes also help cells respond to signals and manage many cell activities. Together, protein kinases and phosphatases keep cellular signaling balanced. When one adds...

gtpases and their regulation

GTPase Molecular Switches and Control

GTPases are molecular switches that help control cell activity. They bind guanosine triphosphate, or GTP, and can change between active and inactive states. This switch-like behavior makes them important in many cell processes. The protein is active when GTP is bound and inactive when guanosine diphosphate, or GDP, is bound. GTPases can also turn themselves off by breaking down GTP into GDP. This built-in control helps cells regulate when the protein is on or off. Their activity is regulated...

Protein regulation by covalent bonds helps control how cells respond to changing conditions. A covalent bond is a strong chemical link, and in this context it can change how a protein behaves. Some regulators work by attaching a chemical group directly to a protein. This covalent change can alter the protein's activity, its location in the cell, or how long it stays active. Because the change is built into the protein itself, it can have a strong effect on cell function. Covalently linked...

protein complexes with interchangeable parts

protein-complexes-with-interchangeable-parts

Modular Protein Complexes in Cells

Protein complexes in cells can be built from interchangeable parts. This modular design lets some complexes share common subunits while still changing their behavior. A well-known example is the ubiquitin ligase complex called SCF. SCF stands for Skp1-Cullin-F-box, and it helps attach ubiquitin, a small protein tag, to target proteins. The core of SCF stays the same, but the F-box protein can change. The interchangeable F-box subunit gives the complex its specificity. Different F-box proteins...

mechanical protein function

Proteins That Generate Cell Movement

Mechanical proteins help cells and tissues move. They turn chemical energy into force and motion. This process is important in many biological systems. These proteins are also called motor proteins. They interact with cell structures and can produce directed movement. In muscle cells, they support contraction. In other cells, they help with transport and shape changes. Mechanical protein function is a key part of how living systems work. It links protein activity to movement at the cellular...

structural protein function

Structural Proteins in Cells and Tissues

Structural proteins help cells and tissues keep their shape and strength. They are an important part of living systems because they provide support where it is needed most. Many structural proteins form fibers or other sturdy forms that resist stretching and wear. These proteins work as building materials in the body and help keep structures stable over time. Examples of structural proteins include collagen, actin, myosin, and keratin. Each one supports a different part of the body, but all...

protein networks

Mapping Protein Interaction Networks

Protein interaction networks show how proteins work together inside a cell. These networks help scientists see which proteins connect with each other and how those links support cell activity. Researchers often use online tools to build and study these networks. The transcript points to IntAct and STRING as examples of resources that can help predict and organize protein interactions. These tools make it easier to compare protein links and look for patterns in the network. Protein networks...

key terms and concepts

Learn how covalent bonds can regulate proteins by changing activity, location, and stability. A clear K12 summary of protein control in cells.

Protein Regulation by Covalent Bonds | JoVE K12

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HS-LS1-3

Protein Regulation by Covalent Bonds

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