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QUESTION 3 Describe post-translational regulation of gene expression with an example. ABC Τ Τ Τ Arial 3 (12pt) 4 T E's Path:p and whmit. Click Save All Answers to save all answers.

Answer 1

Covalent and generally enzymatic modification of proteins following protein biosynthesis is known as post- translational modification. Proteins are synthesized by ribosomes translating mRNA into polypeptide chains, which may then undergo this post translational modification step to form the mature protein product. Post- translational modifications can occur on the amino acid side chains or at the protein's C- or N-terminal. Many eukaryotic proteins also have carbohydrate molecules attached to them in a process called glycosylation, which can promote protein folding and improve stability as well as serving regulatory functions. Attachment of lipid molecules, known as lipidation, often targets a protein or part of a protein attached to the cell membrane. Other forms of post-translational modification consist of cleaving peptide bonds, as in processing a propeptide to a mature form or removing the initiator methionine residue. The formation of disulfide bonds from cysteine residues may also be referred to as a post-translational modification. Post-translational modification is essential to the biological world. Because of the post-translational modification, the protein acquires different conformation and also functional groups which would specify them to various functions. PTMs are important components in cell signaling, as for example when prohormones are converted to hormones.

Specific examples Phosphorylation is a very common mechanism for regulating the activity of enzymes and is the most common post-translational modification. The modification of histone molecules regulates the conversion of heterochromatin DNA to euchromatin DNA and vice-versa. Modification such as acetylation & methylation is the most common modification to the histone proteins. Post-translational modifications regulate the gene expression The activity of several enzymes, like CDKs, mitogens, etc. relies upon phosphorylation and dephosphorylation. Thus, both are types of post-translational modification.