Protein kinase

A protein kinase is an enzyme that transfers phosphate groups, usually from ATP, to proteins. This phosphorylation can alter a protein’s activity, location, stability, or interactions.

Protein phosphorylation: The addition of a phosphate group to a protein, commonly altering its activity or interactions. It is the modification protein kinases catalyze.
Serine: An amino acid whose hydroxyl group can be phosphorylated in proteins. Many protein kinases modify serine residues.
Mitogen-activated protein kinase: A kinase in a signaling cascade that relays extracellular cues to cellular responses. MAP kinases exemplify how successive phosphorylation steps transmit signals.
Protein kinase A: A cyclic-AMP-activated serine/threonine kinase that regulates diverse cellular processes. It is a well-studied example of a kinase controlled by a second messenger.
Edmond H. Fischer: A biochemist who shared the 1992 Nobel Prize for discovering reversible protein phosphorylation. His work with Edwin Krebs established how phosphorylation regulates enzyme activity.
ATP: A nucleotide that supplies energy and phosphate groups for many cellular reactions. Kinases usually transfer ATP’s terminal phosphate to their protein substrates.
Threonine: An amino acid with a hydroxyl group that can accept a phosphate in proteins. Threonine phosphorylation is a common kinase-catalyzed modification.
Cyclin-dependent kinase: A kinase activated by cyclins that regulates progression through the cell cycle. Its phosphorylation of cell-cycle proteins controls division timing.
Tyrosine kinase: A protein kinase that transfers phosphate groups to tyrosine residues. Its substrate class distinguishes it from serine/threonine kinases.
Edwin G. Krebs: A biochemist who shared the 1992 Nobel Prize for discoveries concerning reversible protein phosphorylation. His research identified a kinase-driven mechanism for regulating glycogen breakdown.

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