The occurrence of tissue-specific twitchin isoforms in the mussel Mytilus galloprovincialis

Authors

  • Miho KUSAKA,

    1. Laboratory of Aquatic Molecular Biology and Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657,
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  • Daisuke IKEDA,

    1. Laboratory of Aquatic Molecular Biology and Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657,
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  • Daisuke FUNABARA,

    1. Laboratory of Muscle Biology, Graduate School of Bioresources, Mie University, Tsu, Mie 514-8507, Japan, and
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  • David J HARTSHORNE,

    1. Muscle Biology Group, University of Arizona, Tucson, Arizona 85721, USA
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  • Shugo WATABE

    Corresponding author
    1. Laboratory of Aquatic Molecular Biology and Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657,
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*Tel: 81-3-5841-7520.
Fax: 81-3-5841-8166: Email: awatabe@mail.ecc.u-tokyo.ac.jp

Abstract

ABSTRACT:  The catch state in Mytilus anterior byssus retractor muscle is regulated by phosphorylation and dephosphorylation of twitchin, a member of the titin/connectin superfamily, and involves two serine residues, Ser-1075 (D1) and Ser-4316 (D2). This study was undertaken to examine whether isoforms of twitchin were expressed in various muscles of the mussel Mytilus galloprovincialis by reverse transcription-polymerase chain reaction. Mussel tissues, including both catch and non-catch muscles, contained various twitchin isoforms that all contained the D2 site and the kinase domain. However, sequence alterations were detected around the D1 site, notably a potential deletion of the D1 site. All isoforms from catch muscles contained both the D1 and D2 sites, whereas those from non-catch muscles also expressed the D2 site, but some of them lacked the D1 site. This suggests that the D1 site of twitchin is essential to the mechanism of catch. Genomic DNA analysis revealed that twitchin isoforms are produced by alternative splicing.

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