CRYSTAL-STRUCTURES OF RECOMBINANT HUMAN DIHYDROFOLATE-REDUCTASE COMPLEXED WITH FOLATE AND 5-DEAZAFOLATE
CRYSTAL-STRUCTURES OF RECOMBINANT HUMAN DIHYDROFOLATE-REDUCTASE COMPLEXED WITH FOLATE AND 5-DEAZAFOLATE
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DOI：
10.1021/bi00492a021
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发表时间：
1990-10-09
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：
DAVIES, JF;DELCAMP, TJ;KRAUT, J
1990年7月12日收到的修订稿件摘要：重组人二氢叶酸还原酶的2.3？晶体结构(EC 1.5。1.3，DHFR)被分解为与叶酸的二元络合物(在中性pH下是较差的底物)以及与缓蚀剂5-去氮氟酸酯的二元络合物。抑制剂似乎在N8结合时质子化，而叶酸不质子化。连接17和V8的多肽平面从其在叶酸复合体中的位置旋转允许5-脱氮菊酯质子化的N8与17的主链羰基氢键，从而有助于该酶对5-脱氮菊酯的亲和力比对叶酸的亲和力更大。在这一点上，结合的5-去氮氟酸酯很可能提供了7，8-二氢叶酸结合的模型，此外，类似于叶酸还原的过渡态。由DHFR二元络合物人-5-去氮卓酮和鸡肝-NADPH叠加而成的假想的叶酸还原过渡态模型揭示了叶酸的蝶烷环和NADPH的二氢烟酰胺环的结合位置有1？重叠。二氢叶酸还原酶(5，6，7，8-四氢叶酸：NADP+氧化还原酶，EC 1.5)1.3，DHFR1)催化NADPH连接的7，8-二氢叶酸还原为5，6，7，8-四氢叶酸。该酶也能催化NADPH连接的叶酸还原为7，8-二氢叶酸，但速度较慢，因物种而异。对DHFR的兴趣源于它在几个临床领域的重要性。这个
Revised Manuscript Received July 12, 1990 abstract: The 2.3-Á crystal structure of recombinant human dihydrofolate reductase (EC 1.5. 1.3, DHFR) has been solved as a binary complex with folate (a poor substrate at neutral pH) and also as a binary complex with an inhibitor, 5-deazafolate. The inhibitor appears to be protona ted at N8 on binding, whereas folate is not. Rotation of the peptide plane joining 17 and V8 from its position in the folate complex permits hydrogen bonding of 5-deazafolate’s protonated N8 to the backbone carbonyl of 17, thus contributing to the enzyme’s greater affinity for 5-deazafolate than for folate. In this respect it is likely that bound 5-deazafolate furnishes a model for 7, 8-dihydrofolate binding and, in addition, resembles the transition state for folate reduction. A hypothetical transition-state model for folate reduction, generated by superposition of the DHFR binary complexes human-5-deazafolate and chicken liver-NADPH, reveals a 1-Á overlap of the binding sites for folate’s pteridine ring and the dihydronicotinamide ring of NADPH. It is proposed that this binding-site overlap accelerates the reduction of both folate and 7, 8-dihydrofolate by simultaneously binding substrate and cofactorwith a sub van der Waals separation that is optimal for hydride transfer.Dihydrofolate reductase (5, 6, 7, 8-tetrahydrofolate: NADP+ oxidoreductase, EC 1.5. 1.3, DHFR1) catalyzes the NADPH-linked reduction of 7, 8-dihydrofolate to 5, 6, 7, 8-tetrahydrofolate. The enzyme is alsocapable of catalyzing the NADPH-linked reduction of folate to 7, 8-dihydrofolate, but at a lesser rate, which varies among species. Interest in DHFR stems from its importance inseveral clinical areas. The