A [4Fe–4S]-Fe(CO)(CN)-l-cysteine intermediate is the first organometallic precursor in [FeFe] hydrogenase H-cluster bioassembly

Guodong Rao, Lizhi Tao, Daniel L. M. Suess, R. David Britt

Index: 10.1038/s41557-018-0026-7

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Abstract

Biosynthesis of the [FeFe] hydrogenase active site (the 'H-cluster') requires the interplay of multiple proteins and small molecules. Among them, the radical S-adenosylmethionine enzyme HydG, a tyrosine lyase, has been proposed to generate a complex that contains an Fe(CO)2(CN) moiety that is eventually incorporated into the H-cluster. Here we describe the characterization of an intermediate in the HydG reaction: a [4Fe–4S][(Cys)Fe(CO)(CN)] species, 'Complex A', in which a CO, a CN− and a cysteine (Cys) molecule bind to the unique 'dangler' Fe site of the auxiliary [5Fe–4S] cluster of HydG. The identification of this intermediate—the first organometallic precursor to the H-cluster—validates the previously hypothesized HydG reaction cycle and provides a basis for elucidating the biosynthetic origin of other moieties of the H-cluster.