Regulation by SoxR of mfsA, Which Encodes a Major Facilitator Protein Involved in Paraquat Resistance in Stenotrophomonas maltophilia.
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.
Laboratory of Biotechnology, Chulabhorn Research Institute, Bangkok, 10210, Thailand; Program in Applied Biological Sciences: Environmental Health, Chulabhorn Graduate Institute, Bangkok, 10210, Thailand.
Kriangsuk
K
Srijaruskul
Laboratory of Biotechnology, Chulabhorn Research Institute, Bangkok, 10210, Thailand.
Nisanart
N
Charoenlap
Laboratory of Biotechnology, Chulabhorn Research Institute, Bangkok, 10210, Thailand.
Poommaree
P
Namchaiw
Program in Applied Biological Sciences: Environmental Health, Chulabhorn Graduate Institute, Bangkok, 10210, Thailand.
Sorayut
S
Chattrakarn
Program in Applied Biological Sciences: Environmental Health, Chulabhorn Graduate Institute, Bangkok, 10210, Thailand.
Suparat
S
Giengkam
Laboratory of Biotechnology, Chulabhorn Research Institute, Bangkok, 10210, Thailand; Department of Biotechnology, Faculty of Science, Mahidol University, Bangkok, 10400, Thailand; Center of Emerging Bacterial Infection, Faculty of Science, Mahidol University, Bangkok, 10400, Thailand; Center of Excellence on Environmental Health and Toxicology, Bangkok, Thailand.
Skorn
S
Mongkolsuk
Laboratory of Biotechnology, Chulabhorn Research Institute, Bangkok, 10210, Thailand; Program in Applied Biological Sciences: Environmental Health, Chulabhorn Graduate Institute, Bangkok, 10210, Thailand.
Paiboon
P
Vattanaviboon
D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D004352:Drug Resistance, Microbial; D015964:Gene Expression Regulation, Bacterial; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D010269:Paraquat / Q000494:pharmacology*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D020615:Stenotrophomonas maltophilia / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D015533:Transcriptional Activation
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; D014157:Transcription Factors; C070724:SoxR protein, Bacteria; D010269:Paraquat