Structure and Mechanism of Action of Isopentenylpyrophosphate-Dimethylallylpyrophosphate Isomerase

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• 作者：Johan Wouters ; Yamina Oudjama ; Subhash Ghosh ; Victor Stalon ; Louis Droogmans ; and Eric Oldfield
• 刊名：Journal of the American Chemical Society
• 出版年：2003
• 出版时间：March 19, 2003
• 年：2003
• 卷：125
• 期：11
• 页码：3198 - 3199
• 全文大小：107K
• 年卷期：v.125,no.11(March 19, 2003)
• ISSN：1520-5126

文摘

We have obtained the three-dimensional X-ray crystallographic structure of a C67A mutant Escherichia coli isopentenylpyrophosphate-dimethylallylpyrophosphate isomerase (EC 5.3.3.2) complexed with the bromohydrin of isopentenylpyrophosphate, at 1.93 Å resolution. The overall backbone fold is very similar to that obtained previously for the wild-type enzyme in the presence of a divalent metal cation (Mn²⁺ or Mg²⁺). However, in the new structure, there are two metal binding sites, not just one. The first metal binding site is occupied by Mn²⁺, coordinated to three histidine and two glutamate residues, while the second is occupied by Mg²⁺, coordinated to two bromohydrin-ligand phosphate oxygens, the carbonyl oxygen of A67, a carboxyl oxygen of E87, and two water molecules. The C3 hydroxyl group of the bromohydrin inhibitor is involved in a short hydrogen bond to the carboxyl group of E116, one of the two Mn-bound glutamates. The structure obtained is consistent with a mechanism of action of the enzyme in which the carboxyl group of E116 protonates the double bond in isopentenylpyrophosphate, forming a carbocation, followed by removal of a C2 proton by the thiolate of C67, in the wild-type enzyme. The inhibition of the enzyme by a wide variety of other potent inhibitors is also readily explained on the basis of the bromohydrin inhibitor structure.