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Protein kinase C-related kinase homology region 1 (HR1) Rho-binding domain of Rho-associated coiled-coil containing protein kinase 2 ROCK2 is a serine/threonine protein kinase and was the first identified target of activated RhoA. It plays a role in stress fiber and focal adhesion formation, and is prominently expressed in the brain, heart, and skeletal muscles. It is implicated in vascular and neurological disorders, such as hypertension and vasospasm of the coronary and cerebral arteries. ROCK2 is also activated by caspase-2 cleavage, resulting in thrombin-induced microparticle generation in response to cell activation. Mice deficient in ROCK2 show intrauterine growth retardation and embryonic lethality because of placental dysfunction. ROCK2 contains an N-terminal extension, a catalytic kinase domain, and a long C-terminal extension, which contains a Rho-binding HR1 domain and a pleckstrin homology (PH) domain. ROCK2 is auto-inhibited by HR1 and PH domains interacting with the catalytic domain. HR1 domains are anti-parallel coiled-coil (ACC) domains that bind small GTPases from the Rho family.
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