title: Calcium-mediated regulation of recombinant hybrids of full-length Physarum myosin heavy chain with Physarum/scallop myosin light chains.
abstract: Physarum myosin is a Ca(2+)-binding protein and its activity is inhibited by Ca(2+) In the present study, to clarify the light chains (LCs) from the different species (Physarum and scallop) and to determine the specific Ca(2+)-regulated effects, we constructed hybrid myosins with a Physarum myosin heavy chain (Ph·HC) and Physarum and/or scallop myosin LCs, and examined Ca(2+)-mediated regulation of ATPases and motor activities. In these experiments, it was found that Ca(2+) inhibited motilities and ATPase activities of Physarum hybrid myosin with scallop regulatory light chain (ScRLC) and Physarum essential light chain (PhELC) but could not inhibit those of the Physarum hybrid myosin mutant Ph·HC/ScRLC/PhELC-3A which lacks Ca(2+)-binding ability, indicating that PhELC plays a critical role in Ca(2+)-mediated regulation of Physarum myosin. Furthermore, the effects of Ca(2+) on ATPase activities of Physarum myosin constructs are in the following order: Ph·HC/PhRLC/PhELC > Ph·HC/ScRLC/PhELC > Ph·HC/PhRLC/ScELC > Ph·HC/ScRLC/ScELC, suggesting that the presence of PhRLC and PhELC leads to the greatest Ca(2+) sensitivity of Physarum myosin. Although we did not observe the motilities of Physarum hybrid myosin Ph·HC/PhRLC/ScELC and Ph·HC/ScRLC/ScELC, our results suggest that Ca(2+)-binding to the PhELC may alter the flexibility of the regulatory domain and induce a 'closed' state, which may consequently prevent full activity and force generation.
authors.affiliation: Department of Molecular Physiology and Medical Bioregulation, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi 755-8505, Japan.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Molecular Pharmacology and Oncology, Faculty of Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan.
authors.forename: Hozumi
authors.initials: H
authors.lastname: Kawamichi
authors.affiliation: Research Institute of Pharmaceutical Sciences, Musashino University, Nishitokyo, Tokyo 202-8585, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kohama
authors.affiliation: Department of Molecular Pharmacology and Oncology, Faculty of Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan gacho@gunma-u.ac.jp.
authors.forename: Akio
authors.initials: A
authors.lastname: Nakamura
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D055592:Biophysical Phenomena; D002118:Calcium / Q000378:metabolism; D008958:Models, Molecular; D009068:Movement; D018995:Myosin Heavy Chains / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018994:Myosin Light Chains / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D049897:Pectinidae / Q000235:genetics / Q000378:metabolism*; D010804:Physarum / Q000235:genetics / Q000378:metabolism*; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D018994:Myosin Light Chains; D015800:Protozoan Proteins; D011993:Recombinant Fusion Proteins; D018995:Myosin Heavy Chains; D002118:Calcium
keywords: ATPase activity; Physarum hybrid myosin; actin; calcium; in vitro motility assay