Structures of isobutyryl-CoA dehydrogenase and enzyme-product complex - Comparison with isovaleryl- and short-chain acyl-CoA dehydrogenases
Structures of isobutyryl-CoA dehydrogenase and enzyme-product complex - Comparison with isovaleryl- and short-chain acyl-CoA dehydrogenases
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DOI：
10.1074/jbc.m400034200
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发表时间：
2004-04-16
影响因子：
4.8
通讯作者：
Kim, JJP
中科院分区：
文献类型：
--
作者：
Battaile, KP;Nguyen, TV;Kim, JJP
酰基辅酶A脱氢酶是参与脂肪和氨基酸分解代谢的线粒体黄素蛋白家族。异丁酰辅酶 A 脱氢酶 (IBD) 参与缬氨酸的分解代谢，并催化异丁酰辅酶 A 转化为甲基丙烯酰辅酶 A。带和不带衬底的 IBD 晶体结构已确定为 1.76 埃分辨率。不对称单元包含同源四聚体，其中底物/产物结合在两个单体中。 IBD的整体结构与先前确定的酰基辅酶A脱氢酶的结构相似，由NH2末端α螺旋结构域、内侧β链结构域和C末端α螺旋结构域组成。酶结合配体已被建模为反应产物甲基丙烯酰辅酶A。 Glu-376 相对于结合产物和 FAD 的 C-2-C-3 的位置证实了 Glu-376 是催化碱基。相对于短链酰基辅酶A脱氢酶，IBD具有更短和更宽的底物结合腔，从而允许异丁酰辅酶A底物的最佳结合。在异戊酰辅酶A脱氢酶中观察到的结合腔的显着横向扩张在IBD中没有观察到。在其他酰基辅酶A脱氢酶中定义结合腔一侧的保守酪氨酸或苯丙氨酸在当前结构中被亮氨酸 (Leu-375) 取代。底物结合改变了结合口袋内衬的一些残基的位置以及含有催化谷氨酸和随后的螺旋的环的位置。已对该结构建模了三种临床突变。这些突变不会影响底物结合，但似乎会破坏蛋白质折叠和/或稳定性。
The acyl-CoA dehydrogenases are a family of mitochondrial flavoproteins involved in the catabolism of fatty and amino acids. Isobutyryl-CoA dehydrogenase (IBD) is involved in the catabolism of valine and catalyzes the conversion of isobutyryl-CoA to methacrylyl-CoA. The crystal structure of IBD with and without substrate has been determined to 1.76-Angstrom resolution. The asymmetric unit contains a homotetramer with substrate/product bound in two monomers. The overall structure of IBD is similar to those of previously determined acyl-CoA dehydrogenases and consists of an NH2-terminal alpha-helical domain, a medial beta-strand domain and a C-terminal alpha-helical domain. The enzyme-bound ligand has been modeled in as the reaction product, methacrylyl-CoA. The location of Glu-376 with respect to the C-2-C-3 of the bound product and FAD confirms Glu-376 to be the catalytic base. IBD has a shorter and wider substrate-binding cavity relative to short-chain acyl-CoA dehydrogenase, permitting the optimal binding of the isobutyryl-CoA substrate. The dramatic lateral expansion of the binding cavity seen in isovaleryl-CoA dehydrogenase is not observed in IBD. The conserved tyrosine or phenylalanine that defines a side of the binding cavity in other acyl-CoA dehydrogenases is replaced by a leucine (Leu-375) in the current structure. Substrate binding changes the position of some residues lining the binding pocket as well as the position of the loop containing the catalytic glutamate and subsequent helix. Three clinical mutations have been modeled to the structure. The mutations do not affect substrate binding but instead appear to disrupt protein folding and/or stability.