Biological Regulation by Protein Phosphorylation

Abstract

The biological activity of many proteins is modulated by the phosphorylation of specific sites within the protein. Protein kinases catalyze the transfer of a phosphate group to the protein, while protein phosphatases remove the phosphate group. This reversible modification is utilized by the cell to dynamically regulate proteins that are involved in almost all cellular functions. Protein phosphorylation plays a particularly prominent role in the transduction of extracellular signals. A hormone, neurotransmitter, or growth factor binds to its cell surface receptor and may directly or indirectly activate a protein kinase (or phosphatase) inside the cell, which leads to changes in the phosphorylation states of key regulatory proteins. This cascade of events ultimately results in a functional or phenotypic cellular response (e.g. contraction, release of neurotransmitter, changes in metabolism, or altered gene expression).