Organometallic and radical intermediates reveal mechanism of diphthamide biosynthesis

Diphthamide biosynthesis involves a carbon-carbon bond-forming reaction catalyzed by a radical S-adenosylmethionine (SAM) enzyme that cleaves a carbon-sulfur (C-S) bond in SAM to generate a 3-amino-3-carboxypropyl (ACP) radical. Using rapid freezing, we have captured an organometallic intermediate w...

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Published in:Science (American Association for the Advancement of Science) Vol. 359; no. 6381; p. 1247
Main Authors: Dong, Min, Kathiresan, Venkatesan, Fenwick, Michael K, Torelli, Andrew T, Zhang, Yang, Caranto, Jonathan D, Dzikovski, Boris, Sharma, Ajay, Lancaster, Kyle M, Freed, Jack H, Ealick, Steven E, Hoffman, Brian M, Lin, Hening
Format: Journal Article
Language:English
Published: United States 16.03.2018
Subjects:
Archaeal Proteins - chemistry
Carbon - chemistry
Crystallography, X-Ray
Histidine - analogs & derivatives
Histidine - biosynthesis
Iron - chemistry
Iron-Sulfur Proteins - chemistry
Organometallic Compounds - chemistry
Pyrococcus horikoshii - enzymology
S-Adenosylmethionine - chemistry
ISSN:1095-9203, 1095-9203
Online Access:Get more information
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Summary:Diphthamide biosynthesis involves a carbon-carbon bond-forming reaction catalyzed by a radical S-adenosylmethionine (SAM) enzyme that cleaves a carbon-sulfur (C-S) bond in SAM to generate a 3-amino-3-carboxypropyl (ACP) radical. Using rapid freezing, we have captured an organometallic intermediate with an iron-carbon (Fe-C) bond between ACP and the enzyme's [4Fe-4S] cluster. In the presence of the substrate protein, elongation factor 2, this intermediate converts to an organic radical, formed by addition of the ACP radical to a histidine side chain. Crystal structures of archaeal diphthamide biosynthetic radical SAM enzymes reveal that the carbon of the SAM C-S bond being cleaved is positioned near the unique cluster Fe, able to react with the cluster. Our results explain how selective C-S bond cleavage is achieved in this radical SAM enzyme.
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ISSN:1095-9203
1095-9203
DOI:10.1126/science.aao6595