title: Ca²+-binding properties and regulatory roles of lobster troponin C sites II and IV.
abstract: Invertebrate troponin C typically contains Ca²⁺-specific binding sites, sites II and IV, in the N- and C-terminal domains, respectively. To investigate the roles of these sites for Ca²⁺-dependent regulation of muscle contraction, we generated lobster troponin C mutants, and analyzed their Ca²⁺-binding properties and regulatory effects on actomyosin-tropomyosin Mg-ATPase activity. The results suggest that Ca²⁺ binding to site IV is responsible for regulation at relatively low Ca²⁺ concentrations, while site II has an essential role in full activation at higher Ca²⁺ concentrations.
authors.affiliation: Laboratory of Marine Biotechnology and Microbiology, Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, Japan. tanaka-h@fish.hokudai.ac.jp
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Tanaka
authors.forename: Hiroki
authors.initials: H
authors.lastname: Takahashi
authors.forename: Takao
authors.initials: T
authors.lastname: Ojima
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000737:chemistry*; D008274:Magnesium / Q000737:chemistry*; D008969:Molecular Sequence Data; D009119:Muscle Contraction; D009154:Mutation; D008121:Nephropidae / Q000737:chemistry*; D011485:Protein Binding; D020033:Protein Isoforms; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D019209:Troponin C / Q000737:chemistry*
chemical_list: D020033:Protein Isoforms; D011994:Recombinant Proteins; D019209:Troponin C; D008274:Magnesium; D002118:Calcium
keywords: Arthropod; Ca(2+)-regulation; Invertebrate; Isoform; Muscle; Troponin