Structure and stability of Gyuba, a β-lactoglobulin chimera

Authors

  • Hideaki Ohtomo,

    1. Department of Bioinformatics, Soka University, 1-236 Tangi-cho, Hachioji, Tokyo 192-8577, Japan
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  • Tsuyoshi Konuma,

    1. Department of Bioinformatics, Soka University, 1-236 Tangi-cho, Hachioji, Tokyo 192-8577, Japan
    Current affiliation:
    1. Bioorganic Research Institute, Suntory Foundation for Life Sciences, 1-1-1 Wakayamadai, Shimamoto-cho, Osaka 618-8503, Japan
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  • Hiroko Utsunoiya,

    1. Institute for Health Sciences, Tokushima Bunri University, Yamashiro-cho, Tokushima 770-8514, Japan
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  • Hideaki Tsuge,

    1. Institute for Health Sciences, Tokushima Bunri University, Yamashiro-cho, Tokushima 770-8514, Japan
    2. Faculty of Life Sciences, Kyoto Sangyo University, Kamigamo Motoyama Kita-ku, Kyoto 603-8555, Japan
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  • Masamichi Ikeguchi

    Corresponding author
    1. Department of Bioinformatics, Soka University, 1-236 Tangi-cho, Hachioji, Tokyo 192-8577, Japan
    • Department of Bioinformatics, Soka University, 1-236 Tangi-cho, Hachioji, Tokyo 192-8577, Japan
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Abstract

β-lactoglobulin (LG) contains nine β-strands (strands A–I) and one α-helix. Strands A–H form a β-barrel. At neutral pH, equine LG (ELG) is monomeric, whereas bovine LG (BLG) is dimeric, and the I-strands of its two subunits form an intermolecular β-sheet. We previously constructed a chimeric ELG in which the sequence of the I-strand was replaced with that of BLG. This chimera did not dimerize. For this study, we constructed the new chimera we call Gyuba (which means cow and horse in Japanese). The amino acid sequence of Gyuba includes the sequences of the BLG secondary structures and those of the ELG loops. The crystal structure of Gyuba is very similar to that of BLG and indicates that Gyuba dimerizes via the intermolecular β-sheet formed by the two I-strands. Thus, the entire arrangement of the secondary structural elements is important for LG dimer formation.

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