Protein kinase

The great majority are serine/threonine kinases, which phosphorylate the hydroxyl groups of serines and threonines in their targets.

In the N-terminal extremity of the catalytic domain there is a glycine-rich stretch of residues in the vicinity of a lysine amino acid, which has been shown to be involved in ATP binding.

[10] Serine/threonine protein kinases (EC 2.7.11.1) phosphorylate the OH group of serine or threonine (which have similar side chains).

Activity of these protein kinases can be regulated by specific events (e.g., DNA damage), as well as numerous chemical signals, including cAMP/cGMP, diacylglycerol, and Ca2+/calmodulin.

They play important roles in regulating cell division, cellular differentiation, and morphogenesis.

[citation needed] Ligand binding causes two reactions: Autophosphorylation stabilizes the active conformation of the kinase domain.

The active tyrosine kinase phosphorylates specific target proteins, which are often enzymes themselves.

[citation needed] Tyrosine kinases recruited to a receptor following hormone binding are receptor-associated tyrosine kinases and are involved in a number of signaling cascades, in particular those involved in cytokine signaling (but also others, including growth hormone).

Drugs that inhibit specific kinases are being developed to treat several diseases, and some are currently in clinical use, including Gleevec (imatinib) and Iressa (gefitinib).