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Please use this identifier to cite or link to this item: http://hdl.handle.net/2328/26017

Title: The staphylococcal QacR multidrug regulator binds a correctly spaced operator as a pair of dimers
Authors: Grkovic, Steve
Brown, Melissa Hackett
Schumacher, Maria A
Brennan, Richard G
Skurray, Ronald Anthony
Keywords: Multidrug efflux transporters
Membrane proteins
Bacteria
Issue Date: 2001
Publisher: American Society for Microbiology
Citation: Grkovic, S., Brown, M.H., Schumacher, M.A., Brennan, R.G., and Skurray, R.A., 2001. The staphylococcal QacR multidrug regulator binds a correctly spaced operator as a pair of dimers. Journal of Bacteriology 183(24), 7102-7109.
Abstract: Expression of the Staphylococcus aureus plasmid-encoded QacA multidrug transporter is regulated by the divergently encoded QacR repressor protein. To circumvent the formation of disulfide-bonded degradation products, site-directed mutagenesis to replace the two cysteine residues in wild-type QacR was undertaken. Analysis of a resultant cysteineless QacR derivative indicated that it retained full DNA-binding activities in vivo and in vitro and continued to be fully proficient for the mediation of induction of qacA expression in response to a range of structurally dissimilar multidrug transporter substrates. The cysteineless QacR protein was used in cross-linking and dynamic light-scattering experiments to show that its native form was a dimer, whereas gel filtration indicated that four QacR molecules bound per DNA operator site. The addition of inducing compounds led to the dissociation of the four operator-bound QacR molecules from the DNA as dimers. Binding of QacR dimers to DNA was found to be dependent on the correct spacing of the operator half-sites. A revised model proposed for the regulation of qacA expression by QacR features the unusual characteristic of one dimer of the regulatory protein binding to each operator half-site by a process that does not appear to require the prior self-assembly of QacR into tetramers.
URI: http://hdl.handle.net/2328/26017
ISSN: 0021-9193
Appears in Collections:Biological Sciences - Collected Works

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