Three isoforms of Serine/Threonine kinases, designated αPAK p68, βPAK p65and γPAK p62, have been shown to exhibit a high degree of sequence homologywith the S. cerevisiae kinase Ste 20, involved in pheromone signaling.The α, β and γPAK isoforms complex specifically with Rac 1 and Cdc42 intheir active GTP-bound state, inhibiting their intrinsic GTPase activity leadingto their autophosphorylation. The site of autophosphorylation on αPAK isThr 423, which is in the kinase activation loop. Once phosphorylated andtheir affinity for Rac/Cdc42 reduced, the PAK isoforms disassociate fromthe complex to seek downstream substrates. One such putative substrate isMEK kinase, an upstream effector of MEK-4 which is involved in the JNKsignaling pathway. While the PAK isoforms interact in a GTP-dependentmanner with Rac 1 and Cdc42, they do not interact with Rho.蚂蚁淘在线声明：以上所展示的信息由企业自行提供，内容的真实性、准确性和合法性由发布企业负责。蚂蚁淘在线对此不承担任何保证责任。