Regulation by SoxR of mfsA, Which Encodes a Major Facilitator Protein Involved in Paraquat Resistance in Stenotrophomonas maltophilia

• Published in: PloS one Vol. 10; no. 4; p. e0123699
• Main Authors: Srijaruskul, Kriangsuk, Charoenlap, Nisanart, Namchaiw, Poommaree, Chattrakarn, Sorayut, Giengkam, Suparat, Mongkolsuk, Skorn, Vattanaviboon, Paiboon
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 27-04-2015; Public Library of Science (PLoS)
• Subjects: Agrobacterium tumefaciens; Amino Acid Sequence; Anti-Bacterial Agents - pharmacology; Antibiotics; Antimicrobial agents; Bacteria; Bacterial infections; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Base Sequence; Binding sites; Biotechnology; Cloning; Drug resistance; Drug Resistance, Microbial; Efflux; Environmental health; Gene expression; Gene Expression Regulation, Bacterial; Gene sequencing; Genomes; Homology; Laboratories; Membrane Transport Proteins - genetics; Membrane Transport Proteins - metabolism; Menadione; Molecular Sequence Data; Mutation; Oxidants; Oxidizing agents; Paraquat; Paraquat - pharmacology; Plumbagin; Promoter Regions, Genetic; Protein Binding; Proteins; Pseudomonas aeruginosa; Redox properties; Sensors; SoxR protein; Stenotrophomonas maltophilia; Stenotrophomonas maltophilia - drug effects; Stenotrophomonas maltophilia - genetics; Stenotrophomonas maltophilia - metabolism; Superoxide; Transcription; Transcription Factors - genetics; Transcription Factors - metabolism; Transcriptional Activation; Xanthomonas campestris; Thailand; Bangkok Thailand
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0123699

Stenotrophomonas maltophilia MfsA (Smlt1083) is an efflux pump in the major facilitator superfamily (MFS). Deletion of mfsA renders the strain more susceptible to paraquat, but no alteration in the susceptibility levels of other oxidants is observed. The expression of mfsA is inducible upon challenge with redox cycling/superoxide-generating drug (paraquat, menadione and plumbagin) treatments and is directly regulated by SoxR, which is a transcription regulator and sensor of superoxide-generating agents. Analysis of mfsA expression patterns in wild-type and a soxR mutant suggests that oxidized SoxR functions as a transcription activator of the gene. soxR (smlt1084) is located in a head-to-head fashion with mfsA, and these genes share the -10 motif of their promoter sequences. Purified SoxR specifically binds to the putative mfsA promoter motifs that contain a region that is highly homologous to the consensus SoxR binding site, and mutation of the SoxR binding site abolishes binding of purified SoxR protein. The SoxR box is located between the putative -35 and -10 promoter motifs of mfsA; and this position is typical for a promoter in which SoxR acts as a transcriptional activator. At the soxR promoter, the SoxR binding site covers the transcription start site of the soxR transcript; thus, binding of SoxR auto-represses its own transcription. Taken together, our results reveal for the first time that mfsA is a novel member of the SoxR regulon and that SoxR binds and directly regulates its expression.