protein kinase C conserved region 1 (C1 domain) found in citron Rho-interacting kinase (CRIK) and similar proteins
CRIK, also called serine/threonine-protein kinase 21, is an effector of the small GTPase Rho. It plays an important function during cytokinesis and affects its contractile process. CRIK-deficient mice show severe ataxia and epilepsy as a result of abnormal cytokinesis and massive apoptosis in neuronal precursors. A Down syndrome critical region protein TTC3 interacts with CRIK and inhibits CRIK-dependent neuronal differentiation and neurite extension. CRIK contains a catalytic domain, a central coiled-coil domain, and a C-terminal region containing a Rho-binding domain (RBD), a zinc finger (C1 domain), and a pleckstrin homology (PH) domain, in addition to other motifs. This model corresponds to C1 domain. The C1 domain is a cysteine-rich zinc binding domain that does not bind DNA nor possess structural similarity to conventional zinc finger domains; it contains two separate Zn(2+)-binding sites.