protein kinase C conserved region 1 (C1 domain) found in the Rho-associated coiled-coil containing protein kinase (ROCK) familyROCK is a serine/threonine protein kinase, catalyzing the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. It is also referred to as Rho-associated kinase or simply as Rho kinase. It contains an N-terminal extension, a catalytic kinase domain, and a C-terminal extension, which contains a coiled-coil region encompassing a Rho-binding domain (RBD), a pleckstrin homology (PH) domain and a C1 domain. ROCK is auto-inhibited by the RBD and PH domain interacting with the catalytic domain. It is activated via interaction with Rho GTPases and is involved in many cellular functions including contraction, adhesion, migration, motility, proliferation, and apoptosis. The ROCK subfamily consists of two isoforms, ROCK1 and ROCK2, which may be functionally redundant in some systems, but exhibit different tissue distributions. Both isoforms are ubiquitously expressed in most tissues, but ROCK2 is more prominent in brain and skeletal muscle while ROCK1 is more pronounced in the liver, testes, and kidney. Studies in knockout mice result in different phenotypes, suggesting that the two isoforms do not compensate for each other during embryonic development. 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.