Methionine Sulfoxide Reductases Contribute to Anaerobic Fermentative Metabolism in Bacillus cereus.

Catherine Duport,Jean Armengaud,Béatrice Alpha-Bazin,Jean-Paul Madeira,Mahsa Farjad

doi:10.3390/antiox10050819

Abstract

Reversible oxidation of methionine to methionine sulfoxide (Met(O)) is a common posttranslational modification occurring on proteins in all organisms under oxic conditions. Protein-bound Met(O) is reduced by methionine sulfoxide reductases, which thus play a significant antioxidant role. The facultative anaerobe Bacillus cereus produces two methionine sulfoxide reductases: MsrA and MsrAB. MsrAB has been shown to play a crucial physiological role under oxic conditions, but little is known about the role of MsrA. Here, we examined the antioxidant role of both MsrAB and MrsA under fermentative anoxic conditions, which are generally reported to elicit little endogenous oxidant stress. We created single- and double-mutant Δmsr strains. Compared to the wild-type and ΔmsrAB mutant, single- (ΔmsrA) and double- (ΔmsrAΔmsrAB) mutants accumulated higher levels of Met(O) proteins, and their cellular and extracellular Met(O) proteomes were altered. The growth capacity and motility of mutant strains was limited, and their energy metabolism was altered. MsrA therefore appears to play a major physiological role compared to MsrAB, placing methionine sulfoxides at the center of the B. cereus antioxidant system under anoxic fermentative conditions.

Highlights

It encodes a predicted cytoplasmic MsrA protein consisting of 178 amino acids, with a theoretical molecular mass of 20475 Da
methionine sulfoxide reductase (Msr)-peptide was detected in B. cereus exoproteome whatever the oxygenation conditions, indicating that both MsrA and MsrAB are cytoplasmic proteins. These results suggest that both Msr proteins are expressed at low abundance, and that their levels are decreased when cells are grown in anaerobic conditions compared to aerobic growth conditions
These results indicate that MsrA has a broader substrate range than MsrAB, and that the impact of MsrAB deficiency was minor in the absence of MsrA

Summary

Introduction

Under anaerobiosis and in the absence of a final electron acceptor such as nitrate, B. cereus sustains its growth by producing ATP through mixed acid fermentation

Objectives

Methods

Results

Conclusion