※ MLCK family introduction

    MLCK (myosin light chain kinase) belong to CAMK family and are Ca2+/calmodulin-dependent serine−threonine protein kinase which can phosphorylate the regulatory light chain of mysosin. Skeletal muscle MLCK contains an N-terminal sequence, a protein kinase catalytic core domain and a regulatory segment which consists of an autoinhibitory sequence and a calmodulin binding sequence. The expression size of MLCK in different animal species is related with diverse N-terminal sequence. The MLCKs are activated via binding with calmodulin which is a highly conserved Ca2+-binding protein (1). NMM (nonmuscle myosin) and SMM (smooth muscle myosin) are known substrates of MLCK in vivo. Phosphorylation of RLC on moysin can activate actin-activated myosin ATPase activity which is essential for muscle contraction. In addition, the phosphorylation functions of MLCKs in tracheal, bronchial and gastrointestinal smooth muscle cannot be replaced by others kinases (2).

Reference
1. Stull, J.T., Kamm, K.E. and Vandenboom, R. (2011) Myosin light chain kinase and the role of myosin light chain phosphorylation in skeletal muscle. Arch Biochem Biophys, 510, 120-128. PMID: 21284933
2. Hong, F., Haldeman, B.D., Jackson, D., Carter, M., Baker, J.E. and Cremo, C.R. (2011) Biochemistry of smooth muscle myosin light chain kinase. Arch Biochem Biophys, 510, 135-146. PMID: 21565153