H-NS and Lrp serve as positive modulators of traJ expression from the Escherichia coli plasmid pRK100.
Conjugative transfer of F-like plasmids is a tightly regulated process. The TraJ protein is the main positive activator of the tra operon which encodes products required for conjugative transfer of F-like plasmids. Nucleotide sequence analysis revealed potential Lrp and H-NS binding sites in the traJ regulatory region. Expression of a traJ-lacZ fusion in hns and lrp mutant strains showed that both are positive modulators of traJ expression. Competitive RT-PCR demonstrated that H-NS and Lrp exert their effect at the transcriptional level. Electrophoretic mobility-shift assays showed that H-NS and Lrp proteins bind to the traJ promoter. Conjugative transfer of pRK100 was decreased in hns but not in lrp mutant strains. Together, the results indicate H-NS and Lrp function as activators of traJ transcription.
Starcic-Erjavec
M
M
Department of Biology, Biotechnical Faculty, University of Ljubljana, Vecna pot 111, 1000 Ljubljana, Slovenia.
van Putten
J P M
JP
Gaastra
W
W
Jordi
B J A M
BJ
Grabnar
M
M
Zgur-Bertok
D
D
D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D003433:Crosses, Genetic; D004268:DNA-Binding Proteins / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics; D007700:Kinetics; D051756:Leucine-Responsive Regulatory Protein; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics*; D011506:Proteins / Q000235:genetics* / Q000378:metabolism; D012329:RNA, Bacterial / Q000235:genetics / Q000302:isolation & purification; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors; D001616:beta-Galactosidase / Q000235:genetics
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C031908:H-NS protein, bacteria; C497278:Lrp protein, E coli; D011506:Proteins; D012329:RNA, Bacterial; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D051756:Leucine-Responsive Regulatory Protein; D001616:beta-Galactosidase