unliganded大肠杆菌二氢叶酸还原酶的晶体结构。在绑定Ligand-induced构象变化和协同。
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Bystroff C,德国人J
unliganded大肠杆菌二氢叶酸还原酶的晶体结构。在绑定Ligand-induced构象变化和协同。
生物化学。1991年2月26日,30 (8):2227 - 39。
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1998681 (在PubMed]
- 文摘
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的晶体结构unliganded二氢叶酸还原酶(DHFR)大肠杆菌已经得到解决和改进的R因子19%至2.3 a分辨率晶体形式与每个nonisomorphous之前报道大肠杆菌DHFR晶体结构(柏林时,j . T。、Filman d J。马修斯,d。哈姆林,b . C。和德国人,j .(1982)生物。化学。257年,13650 - 13662;Bystroff C。奥特利,美国J。和酸泡菜,j .(1990)生物化学29日3263 - 3277]。重要的酶蛋白之间的构象变化和每个复合物:辅酶ii +全酶,folate-NADP +三元复杂,甲氨蝶呤(MTX)二进制复杂。最大的变化很小,大约3,其中大部分是小于1的。为简单起见采用哪个域包含两个域描述辅酶ii + 2的磷酸结合位点和结合位点的辅酶和衬底躺在两个域之间。 Binding of either NADP+ or MTX induces a closing of the PABG-binding cleft and realignment of alpha-helices C and F which bind the pyrophosphate of the coenzyme. Formation of the ternary complex from the holoenzyme does not involve further relative domain shifts but does involve a shift of alpha-helix B and a floppy loop (the Met-20 loop) that precedes alpha B. These observations suggest a mechanism for cooperativity in binding between substrate and coenzyme wherein the greatest degree of cooperativity is expressed in the transition-state complex. We explore the idea that the MTX binary complex in some ways resembles the transition-state complex.