[Functional properties and intracellular localization of high molecular weight isoforms of ligh chain myosin kinase].
The vertebrate genetic locus, coding for a Ca2+/calmodulin-dependent enzyme myosin light chain kinase (MLCK), the key regulator of smooth muscle contraction and cell motility, reveals a complex organization. Two MLCK isoforms are encoded by the MLCK genetic locus. Recently identified M(r) 210 kDa MLCK contains a sequence of smooth muscle/non-muscle M(r) 108 kDa MLCK and has an additional N-terminal sequence (Watterson et al., 1995. FEBS Lett. 373 : 217). A gene for an independently expressed non-kinase product KRP (telokin) is located within the MLCK gene (Collinge et al., 1992. Mol. Cell. Biol. 12 : 2359). KRP binds to and regulates the structure of myosin filaments (Shirinsky et al., 1993. J. Biol. Chem. 268 : 16578). Here we compared biochemical properties of MLCK-210 and MLCK-108 and studied intracellular localization of MLCK-210. MLCK-210 was isolated from extract of chicken aorta by immunoprecipitation using specific antibody and biochemically analysed in vitro. MLCK-210 phosphorylated myosin regulatory light chain and heavy meromyosin. The Ca(2+)-dependence and specific activity of MLCK-210 were similar to that of MLCK-108 from turkey gizzard. Using sedimentation assay we demonstrated that MLCK-210 as well as MLCK-108 binds to both actin and myosin filaments. MLCK-210 was localized in smooth muscle cell layers of aortic wall and was found to co-localize with microfilaments in cultured aortic smooth muscle cells.
Chibalina
M V
MV
Institute of Experimental Cardiology, Russian Cardiology Research Centre, Moscow. m.chibalina@cardio.ru
Kudriashov
D S
DS
Shekhonin
B V
BV
Shirinskiĭ
V P
VP
D000818:Animals; D001011:Aorta / Q000201:enzymology; D002642:Chick Embryo; D002645:Chickens; D005895:Gizzard, Avian / Q000201:enzymology; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D008970:Molecular Weight; D009219:Myosin-Light-Chain Kinase / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D014422:Turkeys
D007527:Isoenzymes; D009219:Myosin-Light-Chain Kinase