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Corpus Systématique Animale

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Sequence variations in the surface loop near the nucleotide binding site modulate the ATP turnover rates of molluscan myosins

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  • Cynthia L. Perreault-Micale 1
  • Vassilios N. Kalabokis 1
  • László Nyitray 1
  • Andrew G. Szent-Györgyi 1
  • 1) Department of Biology, Brandeis University, 02254-9110, Waltham, MA, USA

The muscle and species-specific differences in enzymatic activity between Placopecten and Argopecten striated and catch muscle myosins are attributable to the myosin heavy chain. To identify sequences that may modulate these differences, we cloned and sequenced the cDNA encoding the myosin heavy chains of Placopecten striated and catch muscle. Deduced protein sequences indicate two similar isoforms in catch and striated myosins (97% identical); variations arise by differential RNA splicing of five alternative exons from a single myosin heavy chain gene. The first encodes the phosphate-binding loop; the second, part of the ATP binding site; the third, part of the actin binding site; the fourth, the hinge in the rod; and the fifth, a tailpiece found only in the catch muscle myosin heavy chain. Both Placopecten myosin heavy chains are 96% identical to Argopecten myosin heavy chain isoforms. Because subfragment-1 ATPase activities reflect the differences observed in the parent myosins, the motor domain is responsible for the variations in ATPase activities. In addition, data show that differences are due to Vmax and not actin affinity. The sequences of all four myosin heavy chain motor domains diverge only in the flexible surface loop near the nucleotide binding pocket. Thus, the different ATPase activities of four molluscan muscle myosins are likely due to myosin heavy chain sequence variations within the flexible surface loop that forms part of the ATP binding pocket of the motor domain.

Catégories Science-Metrix
  • 1 - health sciences
  • 2 - biomedical research
  • 3 - physiology
Catégories INIST
  • 1 - sciences appliquees, technologies et medecines
  • 2 - sciences biologiques et medicales
  • 3 - sciences biologiques fondamentales et appliquees. psychologie
Catégories Scopus
  • 1 - Life Sciences ; 2 - Biochemistry, Genetics and Molecular Biology ; 3 - Cell Biology
  • 1 - Life Sciences ; 2 - Biochemistry, Genetics and Molecular Biology ; 3 - Biochemistry
  • 1 - Life Sciences ; 2 - Biochemistry, Genetics and Molecular Biology ; 3 - Physiology
Catégories WoS
  • 1 - science ; 2 - cell biology
Identifiant ISTEX

Journal of Muscle Research & Cell Motility

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  • Mollusques
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