Role of Tryptophan Residues in a Class V Chitinase from Nicotiana tabacum

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Tryptophan residues located in the substrate-binding cleft of a class V chitinase from <I>Nicotiana tabacum</I> (NtChiV) were mutated to alanine and phenylalanine (W190F, W326F, W190F/W326F, W190A, W326A, and W190A/W326A), and the mutant enzymes were characterized to define the role of the tryptophans. The mutations of Trp326 lowered thermal stability by 5–7 °C, while the mutations of Trp190 lowered stability only by 2–4 °C. The Trp326 mutations strongly impaired enzymatic activity, while the effects of the Trp190 mutations were moderate. The experimental data were rationalized based on the crystal structure of NtChiV in a complex with (GlcNAc)<SUB>4</SUB>, in which Trp190 is exposed to the solvent and involved in face-to-face stacking interaction with the +2 sugar, while Trp326 is buried inside but interacts with the −2 sugar through hydrophobicity. HPLC analysis of anomers of the enzymatic products suggested that Trp190 specifically recognizes the β-anomer of the +2 sugar. The strong effects of the Trp326 mutations on activity and stability suggest multiple roles of the residue in stabilizing the protein structure, in sugar residue binding at subsite −2, and probably in maintaining catalytic efficiency by providing a hydrophobic environment for proton donor Glu115.

収録刊行物

  • Bioscience, biotechnology, and biochemistry

    Bioscience, biotechnology, and biochemistry 76(4), 778-784, 2012-04-23

    公益社団法人 日本農芸化学会

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各種コード

  • NII論文ID(NAID)
    10030751905
  • NII書誌ID(NCID)
    AA10824164
  • 本文言語コード
    ENG
  • 資料種別
    ART
  • ISSN
    09168451
  • NDL 記事登録ID
    023593084
  • NDL 請求記号
    Z53-G223
  • データ提供元
    CJP書誌  NDL  J-STAGE 
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