Organometallic Complex Formed by an Unconventional Radical S-Adenosylmethionine Enzyme

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• 作者：Min Dong ; Masaki Horitani ; Boris Dzikovski ; Maria-Eirini Pandelia ; Carsten Krebs ; Jack H. Freed ; Brian M. Hoffman ; Hening Lin
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：August 10, 2016
• 年：2016
• 卷：138
• 期：31
• 页码：9755-9758
• 全文大小：279K
• 年卷期：0
• ISSN：1520-5126

文摘

Pyrococcus horikoshii Dph2 (PhDph2) is an unusual radical S-adenosylmethionine (SAM) enzyme involved in the first step of diphthamide biosynthesis. It catalyzes the reaction by cleaving SAM to generate a 3-amino-3-carboxypropyl (ACP) radical. To probe the reaction mechanism, we synthesized a SAM analogue (SAM_CA), in which the ACP group of SAM is replaced with a 3-carboxyallyl group. SAM_CA is cleaved by PhDph2, yielding a paramagnetic (S = 1/2) species, which is assigned to a complex formed between the reaction product, α-sulfinyl-3-butenoic acid, and the [4Fe-4S] cluster. Electron–nuclear double resonance (ENDOR) measurements with ¹³C and ²H isotopically labeled SAM_CA support a π-complex between the C═C double bond of α-sulfinyl-3-butenoic acid and the unique iron of the [4Fe-4S] cluster. This is the first example of a radical SAM-related [4Fe-4S]⁺ cluster forming an organometallic complex with an alkene, shedding additional light on the mechanism of PhDph2 and expanding our current notions for the reactivity of [4Fe-4S] clusters in radical SAM enzymes.