Issue 11, 2023

Binding of exogenous cyanide reveals new active-site states in [FeFe] hydrogenases

Abstract

[FeFe] hydrogenases are highly efficient metalloenyzmes for hydrogen conversion. Their active site cofactor (the H-cluster) is composed of a canonical [4Fe-4S] cluster ([4Fe-4S]H) linked to a unique organometallic di-iron subcluster ([2Fe]H). In [2Fe]H the two Fe ions are coordinated by a bridging 2-azapropane-1,3-dithiolate (ADT) ligand, three CO and two CN ligands, leaving an open coordination site on one Fe where substrates (H2 and H+) as well as inhibitors (e.g. O2, CO, H2S) may bind. Here, we investigate two new active site states that accumulate in [FeFe] hydrogenase variants where the cysteine (Cys) in the proton transfer pathway is mutated to alanine (Ala). Our experimental data, including atomic resolution crystal structures and supported by calculations, suggest that in these two states a third CN ligand is bound to the apical position of [2Fe]H. These states can be generated both by “cannibalization” of CN from damaged [2Fe]H subclusters as well as by addition of exogenous CN. This is the first detailed spectroscopic and computational characterisation of the interaction of exogenous CN with [FeFe] hydrogenases. Similar CN-bound states can also be generated in wild-type hydrogenases, but do not form as readily as with the Cys to Ala variants. These results highlight how the interaction between the first amino acid in the proton transfer pathway and the active site tunes ligand binding to the open coordination site and affects the electronic structure of the H-cluster.

Graphical abstract: Binding of exogenous cyanide reveals new active-site states in [FeFe] hydrogenases

Supplementary files

Article information

Article type
Edge Article
Submitted
04 nov 2022
Accepted
07 feb 2023
First published
08 feb 2023
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2023,14, 2826-2838

Binding of exogenous cyanide reveals new active-site states in [FeFe] hydrogenases

M. A. Martini, K. Bikbaev, Y. Pang, C. Lorent, C. Wiemann, N. Breuer, I. Zebger, S. DeBeer, I. Span, R. Bjornsson, J. A. Birrell and P. Rodríguez-Maciá, Chem. Sci., 2023, 14, 2826 DOI: 10.1039/D2SC06098A

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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