Characterization of a Vibrio vulnificus LysR homologue, HupR, which regulates expression of the haem uptake outer membrane protein, HupA.
In Vibrio vulnificus, the ability to acquire iron from the host has been shown to correlate with virulence. Here, we show that the DNA upstream of hupA (haem uptake receptor) in V. vulnificus encodes a protein in the inverse orientation to hupA (named hupR). HupR shares homology with the LysR family of positive transcriptional activators. A hupA-lacZ fusion contained on a plasmid was transformed into Fur(-), Fur(+)and HupR(-)strains of V. vulnificus. The beta-galactosidase assays and Northern blot analysis showed that transcription of hupA is negatively regulated by iron and the Fur repressor in V. vulnificus. Under low-iron conditions with added haemin, the expression of hupA in the hupR mutant was significantly lower than in the wild-type. This diminished response to haem was detected by both Northern blot and hupA-lacZ fusion analysis. The haem response of hupA in the hupR mutant was restored to wild-type levels when complemented with hupR in trans. These studies suggest that HupR may act as a positive regulator of hupA transcription under low-iron conditions in the presence of haemin.
Litwin
C M
CM
Section of Clinical Immunology, Microbiology and Virology, Salt Lake City, Utah, 84132, USA. Christine.Litwin@path.utah.edu
Quackenbush
J
J
D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000032:analysis / Q000737:chemistry / Q000235:genetics*; D001426:Bacterial Proteins / Q000032:analysis / Q000737:chemistry / Q000235:genetics*; D001483:Base Sequence; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics*; D004268:DNA-Binding Proteins; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects / Q000235:genetics*; D005798:Genes, Bacterial; D006427:Hemin / Q000494:pharmacology; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012329:RNA, Bacterial / Q000032:analysis; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000032:analysis / Q000737:chemistry / Q000235:genetics*; D014158:Transcription, Genetic / Q000187:drug effects; D014733:Vibrio / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C099188:HupA protein, bacteria; D012329:RNA, Bacterial; D014157:Transcription Factors; C070743:hupR1 protein, Rhodobacter capsulatus; D006427:Hemin; C073470:LysR protein, Bacteria