Enzymes, proteins, riboproteins and signaling pathways.


Mitogen activated protein kinases (MAP kinases, MAPKs) are serine/threonine kinases that are activated by mitogens, and act as switch kinases that convert information of increased intracellular tyrosine phosphorylation into serine/threonine phosphorylation. Specific protein kinases transfer a phosphate group from a donor such as ATP to amino acid acceptors in proteins, while protein phosphatases remove the phosphate groups that have been attached by protein kinases. Maximal MAP kinase activity requires phosphorylation of both tyrosine and threonine residues.

The MAPK signaling cascade is:mitogen → MAPKK kinase (MAPKKK) → MAPK kinase (MAPKK) → MAP kinase (MAPK) → signaling

All eukaryotic cells possess multiple MAPK pathways [K], which coordinately regulate diverse cellular activities running the gamut from gene expression, mitosis, and metabolic regulation to motility, survival and apoptosis, and cellular differentiation.

To date, five distinct groups of MAPKs have been characterized in mammals: extracellular signal-regulated kinases (ERKs) 1 and 2 (ERK1/2), c-Jun amino-terminal kinases 1, 2, and 3 (JNKs, or SAPK, stress-activated protein kinases), p38 isoforms α, β, γ, and δ, ERKs 3 and 4, and ERK5 (reviewed in references 25 and 103).[s-fft]

Other MAP kinases include: microtubule associated protein-2 kinase (MAP-2 kinase), myelin basic protein kinase (MBP kinase), ribosomal S6 protein kinase (RSK-kinase) and EGF receptor threonine kinase (ERT kinase). MAP kinases include extracellular-signal regulated kinases (ERKs), with activators that include mitogens: Ras [fft], polypeptide growth factors PDGF, CSF-1, IGF-1, EGF, insulin, and PMA.


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