The staphylococcal QacR multidrug regulator binds a correctly spaced operator as a pair of dimers.

Journal Article (Journal Article)

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.

Full Text

Duke Authors

Cited Authors

  • Grkovic, S; Brown, MH; Schumacher, MA; Brennan, RG; Skurray, RA

Published Date

  • December 2001

Published In

Volume / Issue

  • 183 / 24

Start / End Page

  • 7102 - 7109

PubMed ID

  • 11717268

Pubmed Central ID

  • PMC95558

International Standard Serial Number (ISSN)

  • 0021-9193

Digital Object Identifier (DOI)

  • 10.1128/JB.183.24.7102-7109.2001


  • eng

Conference Location

  • United States