Theoretical Study on Redox Potential Control of Iron-Sulfur Cluster by Hydrogen Bonds: A Possibility of Redox Potential Programming.

Iori Era,Taigo Kamimura,Mitsutaka Okumura,Keigo Cho,Masayoshi Nakano,Yasutaka Kitagawa,Naoka Amamizu,Natsumi Yasuda,Hiromasa Sato

doi:10.3390/molecules26206129

Iori Era, Taigo Kamimura + Show 7 more

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https://doi.org/10.3390/molecules26206129

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Abstract

The effect of hydrogen bonds around the active site of Anabaena [2Fe-2S] ferredoxin (Fd) on a vertical ionization potential of the reduced state (IP(red)) is examined based on the density functional theory (DFT) calculations. The results indicate that a single hydrogen bond increases the relative stability of the reduced state, and shifts IP(red) to a reductive side by 0.31–0.33 eV, regardless of the attached sulfur atoms. In addition, the IP(red) value can be changed by the number of hydrogen bonds around the active site. The results also suggest that the redox potential of [2Fe-2S] Fd is controlled by the number of hydrogen bonds because IP(red) is considered to be a major factor in the redox potential. Furthermore, there is a possibility that the redox potentials of artificial iron-sulfur clusters can be finely controlled by the number of the hydrogen bonds attached to the sulfur atoms of the cluster.

Highlights

In biosystems, the energy is sometimes transferred by electrons with various potential energies in a stepwise manner [1,2,3]
The results indicate that a single [N-H . . . S] or [O-H . . . S] hydrogen bond can shift IP(red) to the reductive side by 0.31–0.33 eV, regardless of the attached sulfur atoms
The value can be changed by the number of hydrogen bonds

Summary

Introduction

The energy is sometimes transferred by electrons with various potential energies in a stepwise manner [1,2,3] For this reason, organisms usually have a variety of electron transfer proteins. Iron–sulfur clusters are often found in the active sites of those electron transfer proteins in a wide range of organisms from bacterium to higher organisms [2]. It has been reported that the electron transfer proteins containing such ironsulfur clusters show a broad range of redox potentials they have the same clusters in the active sites [3]. [4Fe-4S] ferredoxin (Fd) and high potential iron-sulfur protein (HiPIP) are both the electron transfer proteins that have the same 4Fe-4S clusters in the active sites; their redox potentials are −400 ([Fe4 S4 (Cys)4 ]2−/3− ) and. Experimental and theoretical studies have proposed many hypotheses for the mechanism [4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]

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