Thermus thermophilus A4株由来・新規耐熱性β-ガラクトシダーゼおよび基質複合体のX線結晶構造解析  [in Japanese] X-ray Crystallography of a Novel Thermostable β-Galactosidase from Thermus thermophilus A4, and Its Complex Structure with Galactose  [in Japanese]

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Author(s)

Abstract

β-Galactosidase from Thermus thermophilus A4 (A4-β-Gal) is stable at 70°C for 20 h. It belongs to the glycosyl hydrolase family (GF) 42, and enzymes in GF-42 are stable under extreme circumstances such as high temperature or high salt concentration. In order to obtain the structural basis of its reaction mechanism and stability, we conducted X-ray crystallography of the enzyme. We identified the structure of free and galactose-bound A4-β-Gal at 1.6 A and 2.2 A resolution, respectively. The A4-β-Gal has a “flower pot-like” trimeric structure. The monomer structure of A4-β-Gal is composed of three domains. N-terminal domain (domain A) contains a galactose binding site and has a TIM barrel fold. We identified the residues interacting with the galactose. Since Trp182, a residue related to molecular symmetry, constitutes a part of the active site pocket, the trimeric conformation is necessary for A4-β-Gal to retain enzyme activity. We also identified G1u141 and G1u312 as catalytic residues for A4-β-Gal on the basis of the structural evidence. Glu 141 and G1u312 are located close to the C-termini of the fourth and seventh β-strands of the barrel structure, indicating that GF-42 belongs to 4/7 superfamily.

Journal

  • Journal of Applied Glycoscience

    Journal of Applied Glycoscience 49(2), 175-180, 2002-04-01

    The Japanese Society of Applied Glycoscience

References:  17

Cited by:  2

Codes

  • NII Article ID (NAID)
    10008253644
  • NII NACSIS-CAT ID (NCID)
    AN10453916
  • Text Lang
    JPN
  • Article Type
    Journal Article
  • ISSN
    13403494
  • NDL Article ID
    6142457
  • NDL Source Classification
    ZP24(科学技術--化学・化学工業--糖・澱粉)
  • NDL Call No.
    Z17-15
  • Data Source
    CJP  CJPref  NDL  J-STAGE 
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