Rho-associated protein kinases (ROCKs) were originally identified as small GTPase Rho effectors. Later, ROCKs were found actively phosphorylating many actin-binding proteins and intermediate filament proteins to modulate their functions []. Two ROCK isoforms have been identified:ROCK1 (ROKb, p160ROCK) and ROCK2. As major downstream effectors of the small GTPase RhoA, they regulate cellular contraction, motility, morphology, polarity, cell division, and gene expression [, , ].This entry represents the HR1 domain found in Rho-associated protein kinase 2 (ROCK2), which is essential for the formation of stress fibres []. 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 [].
