title: Cooperativity between KorB and TrbA repressors of broad-host-range plasmid RK2.
abstract: The KorB and TrbA proteins of broad-host-range plasmid RK2 are key regulators of the plasmid genes required for conjugative transfer. trbBp is the primary promoter responsible for expression of mating pair formation genes. We show that despite the targets for KorB and TrbA at trbBp being about 165 bp apart, 189 bp upstream of the transcription start point and overlapping the -10 region, respectively, these two proteins show up to 10-fold cooperativity for the repression of trbBp. Deletion analysis of TrbA showed that the C-terminal domain (CTD), which has a high degree of sequence conservation with the CTD of KorA, is required for this cooperativity with KorB. Western blotting demonstrated that the apparently mutual enhancement of repression is not due simply to elevation of repressor level by the presence of the second protein, suggesting that the basis for cooperativity is interaction between KorB and TrbA bound at their respective operators.
authors.affiliation: School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom.
authors.forename: M
authors.initials: M
authors.lastname: Zatyka
authors.forename: L
authors.initials: L
authors.lastname: Bingle
authors.forename: A C
authors.initials: AC
authors.lastname: Jones
authors.forename: C M
authors.initials: CM
authors.lastname: Thomas
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D003227:Conjugation, Genetic; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D011485:Protein Binding; D011815:R Factors / Q000235:genetics*; D012045:Regulatory Sequences, Nucleic Acid; D012097:Repressor Proteins / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C053863:KorB protein, Plasmid RK2; D012097:Repressor Proteins; C098621:trbB protein, Salmonella typhimurium; C076244:trbA protein, E coli