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Báo cáo khoa học: Comparative studies on the functional roles of N- and C-terminal regions of molluskan and vertebrate troponin-I

Vertebrate troponin regulates muscle contraction through alternative bind-ing of the C-terminal region of the inhibitory subunit, troponin-I (TnI), to actin or troponin-C (TnC) in a Ca 2+ -dependent manner. To elucidate the molecular mechanisms of this regulation by molluskan troponin, we com-pared the functional properties of the recombinant fragments of Akazara scallop TnI and rabbit fast skeletal TnI. | ềFEBS Journal Comparative studies on the functional roles of N- and C-terminal regions of molluskan and vertebrate troponin-I Hiroyuki Tanaka1 Yuhei Takeya1 Teppei Doi1 Fumiaki Yumoto2 3 Masaru Tanokura3 Iwao Ohtsuki2 Kiyoyoshi Nishita1 and Takao Ojima1 1 Laboratory of Biotechnology and Microbiology Graduate Schoolof Fisheries Sciences Hokkaido University Japan 2 Laboratory of Physiology The Jikei University Schoolof Medicine Tokyo Japan 3 Department of Applied BiologicalChemistry Graduate Schoolof Agriculturaland Life Sciences University of Tokyo Japan Keywords invertebrate mollusk regulatory mechanism troponin troponin-I Correspondence Takao Ojima Laboratory of Biochemistry and Biotechnology Graduate Schoolof Fisheries Sciences Hokkaido University Hakodate Hokkaido 041-8611 Japan Tel Fax 81 138 408800 E-mail ojima@fish.hokudai.ac.jp Note The nucleotide sequences of cDNAs encoding Akazara scallop 52K-TnI and 19K-Tnl are available in DDBJ EMBL GenBank databases under accession numbers AB206837 and AB206838 respectively Received 24 March 2005 revised 13 June 2005 accepted 15 July 2005 doi 10.1111 j.1742-4658.2005.04866.x Vertebrate troponin regulates muscle contraction through alternative binding of the C-terminal region of the inhibitory subunit troponin-I Tnl to actin or troponin-C TnC in a Ca2 -dependent manner. To elucidate the molecular mechanisms of this regulation by molluskan troponin we compared the functional properties of the recombinant fragments of Akazara scallop TnI and rabbit fast skeletal TnI. The C-terminal fragment of Akaz-ara scallop TnI ATnI232_292 which contains the inhibitory region residues 104-115 of rabbit Tnl and the regulatory TnC-binding site residues 116-131 bound actin-tropomyosin and inhibited actomyosin-tropomyosin Mg-ATPase. However it did not interact with TnC even in the presence of Ca2 . These results indicated that the mechanism involved in the alternative binding of this region was not observed in molluskan troponin. On the .