Methionine sufloxide reductases (Msr) catalize the reduction of methionine sulfoxide (MSO) to methionoine. Among them, free R-methione sulfoxide reductases or MsrCs are sterospecific for the R isomer of MSO. While these enzymes have been studied for their role in protection against oxidative stress, preliminary results from our group suggest that, in E. coli, MsrC might serve as a gene expression regulator. Recombinant expression of EcMsrC impairs growth of several K strains, a phenomenon not observed when expressing heterologous MsrC. This suggests that the aforementioned effect is species-specific and opens the question as to which protein(s) could be potentially interacting with EcMsrC to mediate it. Moreover, preliminary RNA-Seq results showed that EcMsrC overexpression widely alters gene expression, with several genes/operons involved in biosynthetic pathways being downregulated while others associated with nitrate and formate metabolism and anaerobic respiration being upregulated. We hypothesize that EcMsrC could be involved in producing a shift to anaerobic metabolism, and aim to collect more transcriptomics data to test said hypothesis.
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