Dataset Information

Recent Origin of the Methacrylate Redox System in Geobacter sulfurreducens AM-1 through Horizontal Gene Transfer.

ABSTRACT: The origin and evolution of novel biochemical functions remains one of the key questions in molecular evolution. We study recently emerged methacrylate reductase function that is thought to have emerged in the last century and reported in Geobacter sulfurreducens strain AM-1. We report the sequence and study the evolution of the operon coding for the flavin-containing methacrylate reductase (Mrd) and tetraheme cytochrome ? (Mcc) in the genome of G. sulfurreducens AM-1. Different types of signal peptides in functionally interlinked proteins Mrd and Mcc suggest a possible complex mechanism of biogenesis for chromoproteids of the methacrylate redox system. The homologs of the Mrd and Mcc sequence found in ?-Proteobacteria and Deferribacteres are also organized into an operon and their phylogenetic distribution suggested that these two genes tend to be horizontally transferred together. Specifically, the mrd and mcc genes from G. sulfurreducens AM-1 are not monophyletic with any of the homologs found in other Geobacter genomes. The acquisition of methacrylate reductase function by G. sulfurreducens AM-1 appears linked to a horizontal gene transfer event. However, the new function of the products of mrd and mcc may have evolved either prior or subsequent to their acquisition by G. sulfurreducens AM-1.

SUBMITTER: Arkhipova OV

PROVIDER: S-EPMC4427408 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Recent Origin of the Methacrylate Redox System in Geobacter sulfurreducens AM-1 through Horizontal Gene Transfer.

Arkhipova Oksana V OV Meer Margarita V MV Mikoulinskaia Galina V GV Zakharova Marina V MV Galushko Alexander S AS Akimenko Vasilii K VK Kondrashov Fyodor A FA

PloS one 20150511 5

The origin and evolution of novel biochemical functions remains one of the key questions in molecular evolution. We study recently emerged methacrylate reductase function that is thought to have emerged in the last century and reported in Geobacter sulfurreducens strain AM-1. We report the sequence and study the evolution of the operon coding for the flavin-containing methacrylate reductase (Mrd) and tetraheme cytochrome с (Mcc) in the genome of G. sulfurreducens AM-1. Different types of signal ...[more]

PMID: 25962149

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Project description:The monoheme outer membrane cytochrome F (OmcF) from Geobacter sulfurreducens plays an important role in Fe(III) reduction and electric current production. The electrochemical characterization of this cytochrome has shown that its redox potential is modulated by the solution pH (redox-Bohr effect) endowing the protein with the necessary properties to couple electron and proton transfer in the physiological range. The analysis of the OmcF structures in the reduced and oxidized states showed that with the exception of the side chain of histidine 47 (His47), all other residues with protonatable side chains are distant from the heme iron and, therefore, are unlikely to affect the redox potential of the protein. The protonatable site at the imidazole ring of His47 is in the close proximity to the heme and, therefore, this residue was suggested as the redox-Bohr center. In the present work, we tested this hypothesis by replacing the His47 with non-protonatable residues (isoleucine - OmcFH47I and phenylalanine - OmcFH47F). The structure of the mutant OmcFH47I was determined by X-ray crystallography to 1.13 Å resolution and showed only minimal changes at the site of the mutation. Both mutants were 15N-labeled and their overall folding was confirmed to be the same as the wild-type by NMR spectroscopy. The pH dependence of the redox potential of the mutants was measured by cyclic voltammetry. Compared to the wild-type protein, the magnitude of the redox-Bohr effect in the mutants was smaller, but not fully abolished, confirming the role of His47 on the pH modulation of OmcF's redox potential. However, the pH effect on the heme substituents' NMR chemical shifts suggested that the heme propionate P13 also contributes to the overall redox-Bohr effect in OmcF. In physiological terms, the contribution of two independent acid-base centers to the observed redox-Bohr effect confers OmcF a higher versatility to environmental changes by coupling electron/proton transfer within a wider pH range.

Project description:Multiheme cytochromes have been implicated in Geobacter sulfurreducens extracellular electron transfer (EET). These proteins are potential targets to improve EET and enhance bioremediation and electrical current production by G. sulfurreducens. However, the functional characterization of multiheme cytochromes is particularly complex due to the co-existence of several microstates in solution, connecting the fully reduced and fully oxidized states. Over the last decade, new strategies have been developed to characterize multiheme redox proteins functionally and structurally. These strategies were used to reveal the functional mechanism of G. sulfurreducens multiheme cytochromes and also to identify key residues in these proteins for EET. In previous studies, we set the foundations for enhancement of the EET abilities of G. sulfurreducens by characterizing a family of five triheme cytochromes (PpcA-E). These periplasmic cytochromes are implicated in electron transfer between the oxidative reactions of metabolism in the cytoplasm and the reduction of extracellular terminal electron acceptors at the cell's outer surface. The results obtained suggested that PpcA can couple e(-)/H(+) transfer, a property that might contribute to the proton electrochemical gradient across the cytoplasmic membrane for metabolic energy production. The structural and functional properties of PpcA were characterized in detail and used for rational design of a family of 23 single site PpcA mutants. In this review, we summarize the functional characterization of the native and mutant proteins. Mutants that retain the mechanistic features of PpcA and adopt preferential e(-)/H(+) transfer pathways at lower reduction potential values compared to the wild-type protein were selected for in vivo studies as the best candidates to increase the electron transfer rate of G. sulfurreducens. For the first time G. sulfurreducens strains have been manipulated by the introduction of mutant forms of essential proteins with the aim to develop and improve bioelectrochemical technologies.

Dataset Information

Recent Origin of the Methacrylate Redox System in Geobacter sulfurreducens AM-1 through Horizontal Gene Transfer.

Publications

Recent Origin of the Methacrylate Redox System in Geobacter sulfurreducens AM-1 through Horizontal Gene Transfer.

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