抄録
Myosin light chain kinase (MLCK) of smooth muscle consists of the actin-binding domain at the N-terminal, the catalytic domain in the central portion, and the myosin-binding domain at the C-terminal. The kinase activity is mediated by the catalytic domain that phosphorylates the myosin light-chain of 20 kDa (MLC20), activating smooth muscle myosin to interact with actin. Although the regulatory role of the kinase activity is well-established, the role of the non-kinase activity derived from actin-binding and myosin-binding domains remains unknown. We expressed full length MLCK (WT MLCK) as a recombinant protein to examine their effects on the actin-myosin interaction in vitro. We mutated it so as to lose the kinase activity (ΔATP MLCK), followed by the expression. We found that both MT MLCK in the absence of calcium calmodulin and ΔATP MLCK were able to activate the ATPase activity of unphosphorylated smooth muscle myosin. The author will also refer to the effect of arachidonic acid that enhanced the ATPase activity of smooth muscle myosin without phosphorylating myosin ATPase activity and will discuss about the myosin heavy chain consisting of myosin heads as the site of arachidonic action. [J Physiol Sci. 2008;58 Suppl:S31]
