Crystal structure of a novel trimethoprim-resistant dihydrofolate reductase specified in Escherichia coli by R-plasmid R67.
Crystal structure of a novel trimethoprim-resistant dihydrofolate reductase specified in Escherichia coli by R-plasmid R67.
复制标题
大肠杆菌中由 R 质粒 R67 指定的新型耐甲氧苄啶二氢叶酸还原酶的晶体结构。
DOI：
10.1021/bi00363a005
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发表时间：
1986
期刊：
影响因子：
2.9
通讯作者：
Kraut,J
中科院分区：
文献类型：
--
作者：
Matthews,DA;Smith,SL;Baccanari,DP;Burchall,JJ;Oatley,SJ;Kraut,J
摘要：结晶R67二氢叶酸还原酶（DHFR）是一种二聚体分子，具有两个相同的78个氨基酸亚基，每个亚基折叠成1/3桶构象。每个原聚体中三条最长的双链的外表面一起形成第三个双链桶，在亚基界面处有六条双链。酶结构的一个独特特征是，虽然亚基间的双链桶在其大部分表面上是相当规则的，但一个8-π“间隙”贯穿桶的全长，破坏了亚基I中的β-链D和亚基II的相邻相应链之间的潜在氢键。推测该深沟是NADPH结合位点，蛋白质与辅因子之间的结合受该反平行/8桶结构沿着一面的氢键相互作用的调节。提出了R67 DHFR-NADPH-叶酸三元复合物的一个假设模型，该模型与已知的反应立体选择性和2，4-二氨基抑制剂与质粒特异性还原酶的弱结合一致。该模型与鸡DHFR实验确定的结构的几何比较表明，染色体和II型R-质粒特异性酶可能独立地进化出类似的底物还原催化机制。1.3)1是一种非常广泛存在的酶，其催化依赖于NADPH的7，8-二氢叶酸还原为5，6，7，8-四氢叶酸。甲氧苄啶（TMP）选择性地抑制细菌DHFR，并且在过去的15年中已在临床上与磺胺类药物组合用作广谱抗生素。1972年，Fleming等人报道，某些临床菌株
Revised Manuscript Received March 21, 1986 abstract: Crystalline R67 dihydrofolate reductase (DHFR) is a dimeric molecule with two identical 78 amino acid subunits, each folded into a/3-barrel conformation. The outer surfaces of the three longest ß strands in each protomer together form a third ß barrel having six strandsat the subunit interface. A unique feature of the enzyme structure is that while the intersubunit ß barrel is quite regular over most of its surface, an 8-Á “gap” runs the full length of the barrel, disrupting potential hydrogen bonds between/3-strand D in subunit I and the adjacent corresponding strand of subunit II. It is proposed that this deep groove is the NADPH binding site and that the association between protein and cofactor is modulated by hydro-gen-bonding interactions along one face of this antiparallel/8-barrel structure. A hypothetical model is proposed for the R67 DHFR-NADPH-folate ternary complex that is consistent with boththe known reaction stereoselectivity and the weak binding of 2, 4-diamino inhibitors to the plasmid-specified reductase. Geo-metrical comparison of thismodel with an experimentally determined structure for chicken DHFR suggests that chromosomaland type II R-plasmid specified enzymes may have independently evolved similar catalytic machinery for substrate reduction.Dihydrofolate reductase (DHFR; EC 1.5. 1.3) 1 is a very widely occurring enzyme that catalyzes the NADPH-de-pendent reduction of 7, 8-dihydrofolate to 5, 6, 7, 8-tetrahydrofolate. Trimethoprim (TMP) selectively inhibits bacterial DHFR and for the past 15 years has been used clinically in combination with sulfonamides as a broad spectrum antibiotic. In 1972 Fleming et al. reported that certain clinical strains