title: Flexibility of KorA, a plasmid-encoded, global transcription regulator, in the presence and the absence of its operator.
abstract: The IncP (Incompatibility group P) plasmids are important carriers in the spread of antibiotic resistance across Gram-negative bacteria. Gene expression in the IncP-1 plasmids is stringently controlled by a network of four global repressors, KorA, KorB, TrbA and KorC interacting cooperatively. Intriguingly, KorA and KorB can act as co-repressors at varying distances between their operators, even when they are moved to be on opposite sides of the DNA. KorA is a homodimer with the 101-amino acid subunits, folding into an N-terminal DNA-binding domain and a C-terminal dimerization domain. In this study, we have determined the structures of the free KorA repressor and two complexes each bound to a 20-bp palindromic DNA duplex containing its consensus operator sequence. Using a combination of X-ray crystallography, nuclear magnetic resonance spectroscopy, SAXS and molecular dynamics calculations, we show that the linker between the two domains is very flexible and the protein remains highly mobile in the presence of DNA. This flexibility allows the DNA-binding domains of the dimer to straddle the operator DNA on binding and is likely to be important in cooperative binding to KorB. Unexpectedly, the C-terminal domain of KorA is structurally similar to the dimerization domain of the tumour suppressor p53.
authors.affiliation: School of Biosciences, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: Karthik V
authors.initials: KV
authors.lastname: Rajasekar
authors.affiliation: School of Biosciences, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Lovering
authors.affiliation: School of Cancer Studies, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: Felician
authors.initials: F
authors.lastname: Dancea
authors.affiliation: School of Biosciences, Sutton Bonington Campus, University of Nottingham, Nottingham LE12 5RD, UK.
authors.forename: David J
authors.initials: DJ
authors.lastname: Scott
authors.affiliation: School of Physics and Astronomy and Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Harris
authors.affiliation: School of Biosciences, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: Lewis E H
authors.initials: LE
authors.lastname: Bingle
authors.affiliation: EMBL, DESY, 22607 Hamburg, Germany.
authors.forename: Manfred
authors.initials: M
authors.lastname: Roessle
authors.affiliation: School of Biosciences, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Thomas
authors.affiliation: School of Biosciences, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK e.i.hyde@bham.ac.uk.
authors.forename: Eva I
authors.initials: EI
authors.lastname: Hyde
authors.affiliation: School of Biosciences, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK s.a.white@bham.ac.uk.
authors.forename: Scott A
authors.initials: SA
authors.lastname: White
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004269:DNA, Bacterial / Q000737:chemistry / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D009875:Operator Regions, Genetic; D010957:Plasmids / Q000235:genetics; D011485:Protein Binding; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; C090051:KorA protein, bacteria; D012097:Repressor Proteins