CRYSTAL-STRUCTURES OF MEDIUM-CHAIN ACYL-COA DEHYDROGENASE FROM PIG-LIVER MITOCHONDRIA WITH AND WITHOUT SUBSTRATE
CRYSTAL-STRUCTURES OF MEDIUM-CHAIN ACYL-COA DEHYDROGENASE FROM PIG-LIVER MITOCHONDRIA WITH AND WITHOUT SUBSTRATE
复制标题
DOI：
10.1073/pnas.90.16.7523
复制
发表时间：
1993-08-15
影响因子：
11.1
通讯作者：
PASCHKE, R
中科院分区：
文献类型：
--
作者：
KIM, JJP;WANG, M;PASCHKE, R
利用x射线晶体学方法，在2.4埃分辨率下对猪线粒体中链酰基辅酶a脱氢酶及其与底物（产物）复合物的三维结构进行了解析和细化，R因子分别为0.172和0.173。与配体辛烷酰(octenoyl)-辅酶a结合后，整个多肽折叠和四聚体的四级结构基本不变。配体在FAD的直（re）面与酶结合，在酶的两个α -螺旋结构域和β -片结构域之间的缝隙中。硫酯底物的脂肪酰基链埋在多肽内部，3'-AMP部分靠近四聚体酶分子的表面。烷基链取代了天然酶中紧密结合的水分子，硫酯的羰基氧与FAD的ribityl 2'-羟基和Glu-376的主链羰基氧相互作用。脂肪酰基部分的C(α)-C（β）位于黄素和葡萄糖-376的-羧酸之间，支持葡萄糖-376在酶催化的α - β脱氢反应中作为碱提取α质子的作用。Trp-166和Met-165位于酶表面黄素环的负侧（si），表明它们可能参与了与电子转移黄素蛋白的相互作用。Lys-304是在中链酰基辅酶a脱氢酶缺乏症患者中发现的常见突变位点，位于离酶活性位点几乎等于20埃的地方。
The three-dimensional structure of medium-chain acyl-CoA dehydrogenase from pig mitochondria in the native form and that of a complex of the enzyme and a substrate (product) have been solved and refined by x-ray crystallographic methods at 2.4-angstrom resolution to R factors of 0.172 and 0.173, respectively. The overall polypeptide folding and the quaternary structure of the tetramer are essentially unchanged upon binding of the ligand, octanoyl (octenoyl)-CoA. The ligand binds to the enzyme at the rectus (re) face of the FAD in the crevice between the two alpha-helix domains and the beta-sheet domain of the enzyme. The fatty acyl chain of the thioester substrate is buried inside of the polypeptide and the 3'-AMP moiety is close to the surface of the tetrameric enzyme molecule. The alkyl chain displaces the tightly bound water molecules found in the native enzyme and the carbonyl oxygen of the thioester interacts with the ribityl 2'-hydroxyl group of the FAD and the main-chain carbonyl oxygen of Glu-376. The C(alpha)-C(beta) of the fatty acyl moiety lies between the flavin and the gamma-carboxylate of Glu-376, supporting the role of Glu-376 as the base that abstracts the alpha proton in the alpha-beta dehydrogenation reaction catalyzed by the enzyme. Trp-166 and Met-165 are located at the sinister (si) side of the flavin ring at the surface of the enzyme, suggesting that they might be involved in the interactions with electron transferring flavoprotein. Lys-304, the prevalent mutation site found in patients with medium-chain acyl-CoA dehydrogenase deficiency, is located almost-equal-to 20 angstrom away from the active site of the enzyme.