一种来自耐甲氧苄啶细菌的质粒编码二氢叶酸还原酶具有一个新型的D2对称活性位点。
A plasmid-encoded dihydrofolate reductase from trimethoprim-resistant bacteria has a novel D2-symmetric active site.
作者信息
Narayana N, Matthews D A, Howell E E, Nguyen-huu X
机构信息
Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla 92093, USA.
出版信息
Nat Struct Biol. 1995 Nov;2(11):1018-25. doi: 10.1038/nsb1195-1018.
Bacteria expressing R67-plasmid encoded dihydrofolate reductase (R67 DHFR) exhibit high-level resistance to the antibiotic trimethoprim. Native R67 DHFR is a 34,000 M(r) homotetramer which exists in equilibrium with an inactive dimeric form. The structure of native R67 DHFR has now been solved at 1.7 A resolution and is unrelated to that of chromosomal DHFR. Homotetrameric R67 DHFR has an unusual pore, 25 A in length, passing through the middle of the molecule. Two folate molecules bind asymmetrically within the pore indicating that the enzyme's active site consists of symmetry related binding surfaces from all four identical units.
表达R67质粒编码的二氢叶酸还原酶（R67 DHFR）的细菌对抗生素甲氧苄啶表现出高水平抗性。天然R67 DHFR是一种34,000 M（r）的同四聚体，它与无活性的二聚体形式处于平衡状态。天然R67 DHFR的结构现已在1.7 Å分辨率下解析出来，与染色体DHFR的结构无关。同四聚体R67 DHFR有一个不寻常的孔，长25 Å，穿过分子中部。两个叶酸分子不对称地结合在孔内，这表明该酶的活性位点由来自所有四个相同单元的对称相关结合表面组成。
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