The 2.6-A crystal structure of Pseudomonas putida cytochrome P-450.
The 2.6-A crystal structure of Pseudomonas putida cytochrome P-450.
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发表时间：
1985-12
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通讯作者：
T. Poulos;Barry C. FinzelSY;Irwin C. Gunsalusll;G. Wagner;J. Kraut
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作者：
T. Poulos;Barry C. FinzelSY;Irwin C. Gunsalusll;G. Wagner;J. Kraut
恶臭假单胞菌细胞色素 P-450cam 铁、樟脑结合形式的晶体结构已确定，并部分精炼至 2.6 A 时 R = 0.23。单个 414 个氨基酸的多肽链 (Mr = 45,000) 近似于一个三棱柱，最大尺寸约为 60 A，最小尺寸约为 30 A。十二个螺旋段（A 至 L）约占结构的 40%，而反平行 β 对仅占 10% 左右。未暴露的铁原卟啉 IX 夹在两个平行的螺旋之间，分别称为近端螺旋和远端螺旋。血红素铁原子与 Cys 357 提供的轴向硫配体呈五配位，Cys 357 从近端 (L) 螺旋的 N 末端延伸。底物分子 2-bornanone（樟脑）被埋在靠近氧结合位点的血红素远端表面正上方的内部口袋中。除了樟脑分子和邻近的脂肪族和芳香族残基之间的互补疏水接触之外，底物分子还通过 Tyr 96 的侧链羟基和樟脑羰基氧原子之间的氢键固定到位。樟脑的取向使得C5的外表面将接触铁结合的“活化”氧原子以进行立体选择性羟基化。
The crystal structure of Pseudomonas putida cytochrome P-450cam in the ferric, camphor bound form has been determined and partially refined to R = 0.23 at 2.6 A. The single 414 amino acid polypeptide chain (Mr = 45,000) approximates a triangular prism with a maximum dimension of approximately 60 A and a minimum of approximately 30 A. Twelve helical segments (A through L) account for approximately 40% of the structure while antiparallel beta pairs account for only approximately 10%. The unexposed iron protoporphyrin IX is sandwiched between two parallel helices designated the proximal and distal helices. The heme iron atom is pentacoordinate with the axial sulfur ligand provided by Cys 357 which extends from the N-terminal end of the proximal (L) helix. A substrate molecule, 2-bornanone (camphor), is buried in an internal pocket just above the heme distal surface adjacent to the oxygen binding site. The substrate molecule is held in place by a hydrogen bond between the side chain hydroxyl group of Tyr 96 and the camphor carbonyl oxygen atom in addition to complementary hydrophobic contacts between the camphor molecule and neighboring aliphatic and aromatic residues. The camphor is oriented such that the exo-surface of C5 would contact an iron bound, "activated" oxygen atom for stereoselective hydroxylation.