Crystal Structure of P450cin in a Complex with Its Substrate, 1,8-Cineole, a Close Structural Homologue to D-Camphor, the Substrate for P450cam

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• 作者：Yergalem ; T. Meharenna ; Huiying Li ; David B. Hawkes ; Andrew G. Pearson ; James De Voss ; and Thomas L. Poulos
• 刊名：Biochemistry
• 出版年：2004
• 出版时间：July 27, 2004
• 年：2004
• 卷：43
• 期：29
• 页码：9487 - 9494
• 全文大小：525K
• 年卷期：v.43,no.29(July 27, 2004)
• ISSN：1520-4995

文摘

Cytochrome P450cin catalyzes the monooxygenation of 1,8-cineole, which is structurally verysimilar to D-camphor, the substrate for the most thoroughly investigated cytochrome P450, cytochromeP450cam. Both 1,8-cineole and D-camphor are C₁₀ monoterpenes containing a single oxygen atom withvery similar molecular volumes. The cytochrome P450cin-substrate complex crystal structure has beensolved to 1.7 Å resolution and compared with that of cytochrome P450cam. Despite the similarity insubstrates, the active site of cytochrome P450cin is substantially different from that of cytochrome P450camin that the B' helix, essential for substrate binding in many cytochrome P450s including cytochromeP450cam, is replaced by an ordered loop that results in substantial changes in active site topography. Inaddition, cytochrome P450cin does not have the conserved threonine, Thr252 in cytochrome P450cam,which is generally considered as an integral part of the proton shuttle machinery required for oxygenactivation. Instead, the analogous residue in cytochrome P450cin is Asn242, which provides the onlydirect protein H-bonding interaction with the substrate. Cytochrome P450cin uses a flavodoxin-like redoxpartner to reduce the heme iron rather than the more traditional ferredoxin-like Fe₂S₂ redox partner usedby cytochrome P450cam and many other bacterial P450s. It thus might be expected that the redox partnerdocking site of cytochrome P450cin would resemble that of cytochrome P450BM3, which also uses aflavodoxin-like redox partner. Nevertheless, the putative docking site topography more closely resemblescytochrome P450cam than cytochrome P450BM3.