TAILIEUCHUNG - Báo cáo Y học: Coordination structures of Ca21 and Mg21 in Akazara scallop troponin C in solution FTIR spectroscopy of side-chain COO – groups

FTIR spectroscopy has been applied to study the coordination structures of Mg2þ and Ca2þ ions bound in Akazara scallop troponin C (TnC), which contains only a single Ca2þ binding site. The region of the COO – antisymmetric stretch provides information about the coordination modes of COO – groups to the metal ions: bidentate, unidentate, or pseudo-bridging. Two bands were observed at 1584 and 1567 cm21 in the apo state, whereas additional bands were observed at 1543 and 1601 cm21 in the Ca2þ-bound and Mg2þ-bound states, respectively. The intensity of the band at 1567 cm21 in the Mg2þ-bound state was identical. | Eur. J. Biochem. 268 6284-6290 2001 FEBS 2001 Coordination structures of Ca21 and Mg21 in Akazara scallop troponin C in solution FTIR spectroscopy of side-chain COO groups Fumiaki Yumoto1. Masavuki Nara2. Hirovuki Kagi3 Wakana Iwasaki1 Takao Oiima4. Kivovoshi Nishita4 Koji Nagata5 and Masaru Tanokura1 1 Department of Applied Biological Chemistry Graduate School of Agricultural and Life Sciences University of Tokyo Japan 2Laboratory of Chemistry College of Liberal Arts and Sciences Tokyo Medical and Dental University Chiba Japan 3Laboratory for Earthquake Chemistry Graduate School of Science University of Tokyo Japan Department of Marine Bioresources Chemistry Faculty of Fisheries Hokkaido University Hakodate Japan 5Biotechnology Research Center University of Tokyo Japan FTIR spectroscopy has been applied to study the coordination structures of Mg2 and Ca2 ions bound in Akazara scallop troponin C TnC which contains only a single Ca2 binding site. The region of the COO-antisymmetric stretch provides information about the coordination modes of COO- groups to the metal ions bidentate unidentate or pseudo-bridging. Two bands were observed at 1584 and 1567 cm21 in the apo state whereas additional bands were observed at 1543 and 1601 cm21 in the Ca2 -bound and Mg2 -bound states respectively. The intensity of the band at 1567 cm21 in the Mg2 -bound state was identical to that in the apo state. Therefore the sidechain COO- group of Glu142 at the 12th position in the Ca2 -binding site coordinates to Ca2 in the bidentate mode but does not interact with Mg2 directly. A slight upshift of COO- antisymmetric stretch due to Asp side-chains was also observed upon Mg2 and Ca2 binding. This indicates that the COO- groups of Asp131 and Asp133 interact with both Ca2 and Mg2 in the pseudo-bridging mode. Therefore the present study directly demonstrated that the coordination structure of Mg2 was different from that of Ca2 in the Ca2 -binding site. In contrast to vertebrate TnC most of .

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