期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2009
卷号：106
期号：49
页码：20687-20692
DOI：10.1073/pnas.0907398106
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Mycobacterium tuberculosis (Mtb) produces a variety of methyl-branched lipids that serve important functions, including modulating the immune response during pathogenesis and contributing to a robust cell wall that is impermeable to many chemical agents. Here, we report characterization of Mtb CYP124 (Rv2266) that includes demonstration of preferential oxidation of methyl-branched lipids. Spectrophotometric titrations and analysis of reaction products indicate that CYP124 tightly binds and hydroxylates these substrates at the chemically disfavored {omega}-position. We also report X-ray crystal structures of the ligand-free and phytanic acid-bound protein at a resolution of 1.5 A and 2.1 A, respectively, which provide structural insights into a cytochrome P450 with predominant {omega}-hydroxylase activity. The structures of ligand-free and substrate-bound CYP124 reveal several differences induced by substrate binding, including reorganization of the I helix and closure of the active site by elements of the F, G, and D helices that bind the substrate and exclude solvent from the hydrophobic active site cavity. The observed regiospecific catalytic activity suggests roles of CYP124 in the physiological oxidation of relevant Mtb methyl-branched lipids. The enzymatic specificity and structures reported here provide a scaffold for the design and testing of specific inhibitors of CYP124.
