文章基本信息

标题：Organometallic mechanism of action and inhibition of the 4Fe-4S isoprenoid biosynthesis protein GcpE (IspG)
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作者：Weixue Wang ; Jikun Li ; Ke Wang 等
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：2010
卷号：107
期号：25
页码：11189-11193
DOI：10.1073/pnas.1000264107
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：We report the results of a series of chemical, EPR, ENDOR, and HYSCORE spectroscopic investigations of the mechanism of action (and inhibition) of GcpE, E-1-hydroxy-2-methyl-but-2-enyl-4-diphosphate (HMBPP) synthase, also known as IspG, an Fe4S4 cluster-containing protein. We find that the epoxide of HMBPP when reduced by GcpE generates the same transient EPR species as observed on addition of the substrate, 2-C-methyl-D-erythritol-2, 4-cyclo-diphosphate. ENDOR and HYSCORE spectra of these transient species (using 2H, 13C and 17O labeled samples) indicate formation of an Fe-C-H containing organometallic intermediate, most likely a ferraoxetane. This is then rapidly reduced to a ferracyclopropane in which the HMBPP product forms an{eta} 2-alkenyl{pi} - (or{pi} /{sigma}) complex with the 4th Fe in the Fe4S4 cluster, and a similar "metallacycle" also forms between isopentenyl diphosphate (IPP) and GcpE. Based on this metallacycle concept, we show that an alkyne (propargyl) diphosphate is a good (Ki [~] 300 nM) GcpE inhibitor, and supported again by EPR and ENDOR results (a 13C hyperfine coupling of [~]7 MHz), as well as literature precedent, we propose that the alkyne forms another{pi} /{sigma} metallacycle, an{eta} 2-alkynyl, or ferracyclopropene. Overall, the results are of broad general interest because they provide new mechanistic insights into GcpE catalysis and inhibition, with organometallic bond formation playing, in both cases, a key role.
关键词：4Fe-4S protein ; GcpE (IspG) ; metallacycle