Rho-associated protein kinase 1 (ROCK1), also known as Rho kinase beta, is a serine-threonine protein kinase that plays an important role in cellular apoptosis, growth, cell motility and cell contraction. ROCK1 shares an overall 65% homology in amino acid sequence with ROCK2. The ROCK1 and ROCK2 isoforms are products of two separate genes. Both ROCK1 and ROCK2 are downstream targets of the Rho A small GTP-binding protein. As downstream effectors of RhoA, ROCK1 and ROCK2 mediate changes in the actin cytoskeleton via phosphorylation of target proteins such as the MBS subunit of MLCP, MLC, ERM proteins, protein LIM kinase and adducin.