Cofactor-induced conformational rearrangements establish a catalytically competent active site and a proton relay conduit in FabG
Cofactor-induced conformational rearrangements establish a catalytically competent active site and a proton relay conduit in FabG
复制标题
DOI：
10.1016/j.str.2004.02.008
复制
发表时间：
2004-03-01
期刊：
影响因子：
5.7
通讯作者：
White, SW
中科院分区：
文献类型：
--
作者：
Price, AC;Zhang, YM;White, SW
β-酮酰基-酰基载体蛋白还原酶（FabG）是II型脂肪酸合酶系统中的关键组分。大肠杆菌FabG和FabG [Y151F]突变体与NADP（H）二元复合物的结构表明，辅助因子结合伴随着重要的机械构象变化。活性位点Ser-Tyr-Lys三联体被重新定位成催化活性星座，并且由核糖羟基、Ser-Tyr-Lys三联体和四个水分子组成的氢键网络产生质子线以补充催化期间提供的酪氨酸质子。此外，FabG中的无序环在复合物中形成了一个子结构，该子结构形成了活性位点的入口。一个关键的观察结果是，辅因子的烟酰胺部分在FabG [Y151F]中是无序的。NADP（H）复合物，Tyr151似乎是高亲和力辅因子结合所必需的。生化数据证实FabG [Y151F]在NADPH结合方面存在缺陷。最后，与所观察到的负协同FabG的结构变化进行了描述。
beta-Ketoacyl-acyl carrier protein reductase (FabG) is a key component in the type II fatty acid synthase system. The structures of Escherichia coli FabG and the FabG[Y151F] mutant in binary complexes with NADP(H) reveal that mechanistically important conformational changes accompany cofactor binding. The active site Ser-Tyr-Lys triad is repositioned into a catalytically competent constellation, and a hydrogen bonded network consisting of ribose hydroxyls, the Ser-Tyr-Lys triad, and four water molecules creates a proton wire to replenish the tyrosine proton donated during catalysis. Also, a disordered loop in FabG forms a substructure in the complex that shapes the entrance to the active site. A key observation is that the nicotinamide portion of the cofactor is disordered in the FabG [Y151F](.)NADP(H) complex, and Tyr151 appears to be necessary for high-affinity cofactor binding. Biochemical data confirm that FabG[Y151F] is defective in NADPH binding. Finally, structural changes consistent with the observed negative cooperativity of FabG are described.