Issue 13, 2023

Redox tuning of the H-cluster by second coordination sphere amino acids in the sensory [FeFe] hydrogenase from Thermotoga maritima

Abstract

[FeFe] hydrogenases are exceptionally active catalysts for the interconversion of molecular hydrogen with protons and electrons. Their active site, the H-cluster, is composed of a [4Fe–4S] cluster covalently linked to a unique [2Fe] subcluster. These enzymes have been extensively studied to understand how the protein environment tunes the properties of the Fe ions for efficient catalysis. The sensory [FeFe] hydrogenase (HydS) from Thermotoga maritima has low activity and displays a very positive redox potential for the [2Fe] subcluster compared to that of the highly active prototypical enzymes. Using site directed mutagenesis, we investigate how second coordination sphere interactions of the protein environment with the H-cluster in HydS influence the catalytic, spectroscopic and redox properties of the H-cluster. In particular, mutation of the non-conserved serine 267, situated between the [4Fe–4S] and [2Fe] subclusters, to methionine (conserved in prototypical catalytic enzymes) gave a dramatic decrease in activity. Infra-red (IR) spectroelectrochemistry revealed a 50 mV lower redox potential for the [4Fe–4S] subcluster in the S267M variant. We speculate that this serine forms a hydrogen bond to the [4Fe–4S] subcluster, increasing its redox potential. These results demonstrate the importance of the secondary coordination sphere in tuning the catalytic properties of the H-cluster in [FeFe] hydrogenases and reveal a particularly important role for amino acids interacting with the [4Fe–4S] subcluster.

Graphical abstract: Redox tuning of the H-cluster by second coordination sphere amino acids in the sensory [FeFe] hydrogenase from Thermotoga maritima

Supplementary files

Article information

Article type
Edge Article
Submitted
22 Nov 2022
Accepted
27 Feb 2023
First published
27 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, 3682-3692

Redox tuning of the H-cluster by second coordination sphere amino acids in the sensory [FeFe] hydrogenase from Thermotoga maritima

N. Chongdar, P. Rodríguez-Maciá, E. J. Reijerse, W. Lubitz, H. Ogata and J. A. Birrell, Chem. Sci., 2023, 14, 3682 DOI: 10.1039/D2SC06432D

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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