title: Two isoforms of regulatory light chain of abalone smooth muscle myosin.
abstract: Abalone myosin contains two kinds of light chain, regulatory light chain (LC2) and essential light chain (LC1) according to SDS-PAGE. Three distinct light chain bands were observed on polyacrylamide gel electrophoresis of purified abalone myosin in the presence of urea (urea-PAGE). The slower two components showed had mobility on SDS-PAGE and they also showed regulatory activity as the regulatory light chain. They were termed LC2-a and LC2-b in order of increasing mobility on urea-PAGE and isolated by DE-32 ion exchange column chromatography in the presence 8 M urea. The ratio of LC2-a and LC2-b in the central portion of adductor muscle of abalone (LC2-a: LC2-b = 7:3) was different from that (1:1) in the peripheral portion. These results suggest that the two light chains are isoforms of the regulatory light chain. The amino acid compositions of LC2-a and LC2-b were very similar to each other except for the Cys content. The UV absorption spectra were also quite similar, as were the UV difference absorption spectra induced by Ca2+. Phosphorylation was not detectable with the myosin light chain kinase of chicken gizzard. The Ca2+ concentration dependencies of Mg-ATPase activity of LC2-a or LC2-b hybridized abalone myosin (a-myosin, b-myosin) were similar to each other in the absence of rabbit F-actin, but differed in the presence of actin. The b-myosin had a higher maximum value of actomyosin ATPase activity and a lower apparent binding constant of actin and myosin than a-myosin.(ABSTRACT TRUNCATED AT 250 WORDS)
authors: Hokkaido University of Education, Asahikawa.
authors: T
authors: T
authors: Asakawa
authors: N
authors: N
authors: Azuma
mesh_terms: D000199:Actins / Q000378:metabolism; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology; D011232:Chemical Precipitation; D004591:Electrophoresis, Polyacrylamide Gel; D000070559:Gizzard, Non-avian / Q000201:enzymology; D007536:Isomerism; D008974:Mollusca; D009130:Muscle, Smooth / Q000378:metabolism*; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism; D009218:Myosins / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D013056:Spectrophotometry, Ultraviolet
chemical_list: D000199:Actins; D000596:Amino Acids; D009219:Myosin-Light-Chain Kinase; D017301:Ca(2+) Mg(2+)-ATPase; D009218:Myosins; D002118:Calcium