Redox Behavior of the S-Adenosylmethionine (SAM)-Binding Fe-S Cluster in Methylthiotransferase RimO, toward Understanding Dual SAM Activity

Thibaut Molle; Yohann Moreau; Martin Clémancey; Farhad Forouhar; Jean-Luc Ravanat; Nicolas Duraffourg; Vincent Fourmond; Jean-Marc Latour; Serge Gambarelli; Etienne Mulliez; Mohamed Atta

doi:10.1021/acs.biochem.6b00597

Journal articles

Redox Behavior of the S-Adenosylmethionine (SAM)-Binding Fe-S Cluster in Methylthiotransferase RimO, toward Understanding Dual SAM Activity

Thibaut Molle ¹ Yohann Moreau ¹ Martin Clémancey ¹ Farhad Forouhar ^{2, 3} Jean-Luc Ravanat ⁴ Nicolas Duraffourg ¹ Vincent Fourmond ⁵ Jean-Marc Latour ¹ Serge Gambarelli ⁶ Etienne Mulliez ^{1, *} Mohamed Atta ^{1, *}

* Corresponding author

1 LCBM - UMR 5249 - Laboratoire de Chimie et Biologie des Métaux

2 Department of Biological Sciences, Columbia University, New York, New York, USA.

3 Northeast Structural Genomics Consortium

4 LAN - Laboratoire Lésions des Acides Nucléiques

SCIB - UMR E3 - Service de Chimie Inorganique et Biologique : DSM/INAC/SCIB

5 BIP - Bioénergétique et Ingénierie des Protéines

6 SCIB - UMR E3 - Service de Chimie Inorganique et Biologique

Abstract : RimO, a radical-S-adenosylmethionine (SAM) enzyme, catalyzes the specific C3 methylthiolation of the D89 residue in the ribosomal S12 protein. Two intact iron–sulfur clusters and two SAM cofactors both are required for catalysis. By using electron paramagnetic resonance, Mössbauer spectroscopies, and site-directed mutagenesis, we show how two SAM molecules sequentially bind to the unique iron site of the radical-SAM cluster for two distinct chemical reactions in RimO. Our data establish that the two SAM molecules bind the radical-SAM cluster to the unique iron site, and spectroscopic evidence obtained under strongly reducing conditions supports a mechanism in which the first molecule of SAM causes the reoxidation of the reduced radical-SAM cluster, impeding reductive cleavage of SAM to occur and allowing SAM to methylate a HS– ligand bound to the additional cluster. Furthermore, by using density functional theory-based methods, we provide a description of the reaction mechanism that predicts the attack of the carbon radical substrate on the methylthio group attached to the additional [4Fe-4S] cluster.

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Journal articles

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Chemical Sciences

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Submitted on : Monday, December 12, 2016 - 3:59:14 PM
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Redox Behavior of the S-Adenosylmethionine (SAM)-Binding Fe-S Cluster in Methylthiotransferase RimO, toward Understanding Dual SAM Activity

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Redox Behavior of the S-Adenosylmethionine (SAM)-Binding Fe-S Cluster in Methylthiotransferase RimO, toward Understanding Dual SAM Activity

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