Radical SAM Enzyme HydE Generates Adenosylated Fe(I) Intermediates En Route to the [FeFe]-Hydrogenase Catalytic H-Cluster.
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The H-cluster of [FeFe]-hydrogenase consists of a [4Fe-4S]H-subcluster linked by a cysteinyl bridge to a unique organometallic [2Fe]H-subcluster assigned as the site of interconversion between protons and molecular hydrogen. This [2Fe]H-subcluster is assembled by a set of Fe-S maturase enzymes HydG, HydE and HydF. Here we show that the HydG product [FeII(Cys)(CO)2(CN)] synthon is the substrate of the radical SAM enzyme HydE, with the generated 5'-deoxyadenosyl radical attacking the cysteine S to form a C5'-S bond concomitant with reduction of the central low-spin Fe(II) to the Fe(I) oxidation state. This leads to the cleavage of the cysteine C3-S bond, producing a mononuclear [FeI(CO)2(CN)S] species that serves as the precursor to the dinuclear Fe(I)Fe(I) center of the [2Fe]H-subcluster. This work unveils the role played by HydE in the enzymatic assembly of the H-cluster and expands the scope of radical SAM enzyme chemistry.
author list (cited authors)
Tao, L., Pattenaude, S. A., Joshi, S., Begley, T. P., Rauchfuss, T. B., & Britt, R. D.
complete list of authors
Tao, Lizhi||Pattenaude, Scott A||Joshi, Sumedh||Begley, Tadhg P||Rauchfuss, Thomas B||Britt, R David