C-terminal kinase domain of the Large Serine/Threonine Kinase and Rho Guanine Nucleotide Exchange Factor, Kalirin
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. Kalirin, also called Duo or Duet, is a large multidomain protein containing a series of spectrin-like repeats, two each of RhoGEF and SH3 domains, an immunoglobulin-like (Ig) domain and a C-terminal kinase. As a GEF, it activates Rac1, RhoA, and RhoG. It is highly expressed in neurons and is required for spine formation. The kalirin gene produces at least 10 isoforms from alternative promoter use and splicing. Of the major isoforms (Kalirin-7, -9, and -12), only kalirin-12 contains the C-terminal kinase domain. Kalirin-12 is highly expressed during embryonic development and it plays an important role in axon outgrowth. The Kalirin 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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