GLOSSARY

Protein phosphorylation is the reversible addition of a phosphate group (from ATP) to serine, threonine, or tyrosine residues of proteins by kinases; by changing a protein’s shape and charge, it alters its activity, location, or interactions, making it the most common mechanism of rapid protein regulation and the cell’s “on–off switch”.

Components

• Kinases: add phosphate; more than 500 kinase genes in humans (the kinome).
• Phosphatases: remove phosphate, returning the protein to its original state.
• The balance between the two determines the phosphorylation state and thus protein activity.

Hormonal Examples