Catalytic domain of the Serine/Threonine kinase, Calcium/calmodulin-dependent protein kinase Type I alpha
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. CaMKs are multifunctional calcium and calmodulin (CaM) stimulated STKs involved in cell cycle regulation. The CaMK family includes CaMKI, CaMKII, CaMKIV, and CaMK kinase (CaMKK). In vertebrates, there are four CaMKI proteins encoded by different genes (alpha, beta, gamma, and delta), each producing at least one variant. CaMKs contain an N-terminal catalytic domain and a C-terminal regulatory domain that harbors a CaM binding site. CaMKI proteins are monomeric and they play pivotal roles in the nervous system, including long-term potentiation, dendritic arborization, neurite outgrowth, and the formation of spines, synapses, and axons. In addition, they may be involved in osteoclast differentiation and bone resorption. The CaMKI-alpha subfamily is part of a larger superfamily that includes the catalytic domains of other protein kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.