Question

Please compare and contrast protein regulation by covalent modification vs. allosteric regulation. I am looking for at least one similarity and three differences. The similarity cannot be that they are both types of regulation. This is given to you in the question. And you should include a complete discussion of protein regulation by covalent modification vs allosteric regulation.

You should include:

1. What binds to the molecule

2. Where the ligand (substance that binds) binds to the molecule

3. How the regulation is reversed.

Answer 1

Proteins are the building blocks of human body. The protein is synthesized in the cytoplasm or rough endoplasmic reticulum through the process of translation. Enzyme is also a protein. For the proper functioning of this proteins, some of the modifications are needed. One of this modification is the covalent modification. it will modify the activity of enzymes and many other proteins positively for the proper action.

Allosteric regulation (or allosteric control) is the regulation of an enzyme, but not all protein. By controlling the enzyme, indirectly control the rate of enzymatic reactions. Here both, activation or inhibition can happens based on which molecule is binding to the allosteric site. It is the regulation of an enzyme by binding an effector molecule at a site other than the enzyme's active site.

Covalent modification	Allosteric regulation
Enzyme‐catalyzed alterations of synthesized proteins (including enzymes).	Modifications of an enzyme.
Change the chemical properties of the site.	Conformational change happens to enzyme.
Modification is mainly for the activation of proteins.	Based on the effector molecule, either activation or inhibition.
Give functional moiety that modifies the properties of the proteins.	Either activator or repressor molecule is bind to the allosteric site.
Chemical change happens to the protein.	conformational or electrostatic changes happens to the protein.
Major covalent modification is phosphorylation

Both regulation is entirely different regulation. But both regulation can be reversible most cases. Allosteric regulation is completely reversible and the covalent modification may be reversible, but not in all cases.

The most common reversible covalent modification is the addition and removal of phosphate groups through the processes of phosphorylation and dephosphorylation.

In allosteric regulation,  molecule binds reversibly to the protein altering its conformation, which in turn alters the protein's structure, its location within the cell, its activity.