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Catalytic domain of the Serine/Threonine Kinase, p21-activated kinase 1 STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. PAK1 is important in the regulation of many cellular processes including cytoskeletal dynamics, cell motility, growth, and proliferation. Although PAK1 has been regarded mainly as a cytosolic protein, recent reports indicate that PAK1 also exists in significant amounts in the nucleus, where it is involved in transcription modulation and in cell cycle regulatory events. PAK1 is also involved in transformation and tumorigenesis. Its overexpression, hyperactivation and increased nuclear accumulation is correlated to breast cancer invasiveness and progression. Nuclear accumulation is also linked to tamoxifen resistance in breast cancer cells. PAK1 belongs to the group I PAKs, which contain a PBD (p21-binding domain) overlapping with an AID (autoinhibitory domain), a C-terminal catalytic domain, SH3 binding sites and a non-classical SH3 binding site for PIX (PAK-interacting exchange factor). PAKs are Rho family GTPase-regulated kinases that serve as important mediators in the function of Cdc42 (cell division cycle 42) and Rac. The PAK subfamily is part of a larger superfamily that includes the catalytic domains of other protein STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase. |
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