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首页> 外文期刊>Biochemistry >CRYSTAL STRUCTURE IMPLIES THAT CYCLOPHILIN PREDOMINANTLY CATALYZES THE TRANS TO CIS ISOMERIZATION
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CRYSTAL STRUCTURE IMPLIES THAT CYCLOPHILIN PREDOMINANTLY CATALYZES THE TRANS TO CIS ISOMERIZATION

机译：晶体结构暗示环青霉素主要催化转化为CIS的异构化反应

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摘要

The crystal structure of human recombinant cyclophilin A complexed with a substrate of succinyl-Ala-Ala-Pro-Phe-p-nitroanilide (AAPF) has been determined and refined to an R-factor of 0.189 at 2.4 Angstrom resolution. The structure revealed only the cis form of the substrate bound to cyclophilin A in a stoichiometry of 1:1. This binding ratio is different from the structure of cyclophilin A complexed with the tetrapeptide N-acetyl-Ala-Ala-Pro-Ala-amidomethylcourmarin. Model docking revealed that the trans form of AAPF does not fit into the active site. The observation that only the cis form of AAPF binds to cyclophilin A implies that cyclophilin A predominantly catalyzes the trans to cis isomerization of a peptidyl-prolyl amide bond. On the basis of the structure, it is proposed that Arg55 hydrogen-bonds to the nitrogen to deconjugate the resonance of the prolyl amide bond and thus facilitates the cis-trans rotation.
机译：已经确定了与琥珀酰-丙氨酸-丙氨酸-脯氨酸-苯丙氨酸-对硝基苯胺（AAPF）底物复合的人重组亲环蛋白A的晶体结构，并在2.4埃分辨率下将其精制为0.189的R因子。该结构仅显示化学计量比为1：1的与亲环蛋白A结合的底物的顺式形式。该结合比率不同于与四肽N-乙酰基-Ala-Ala-Pro-Ala-酰胺基甲基古马酚复合的亲环蛋白A的结构。模型对接表明，AAPF的反式不适合活性位点。仅AAPF的顺式形式结合亲环蛋白A的观察结果表明，亲环蛋白A主要催化肽基-脯氨酰胺键的反式至顺式异构化。根据该结构，提出Arg55氢键合到氮上以使脯氨酰胺键的共振解共轭，从而促进顺反旋转。

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