Open AccessStructural and Biochemical Analysis of the Pentapeptide Repeat Protein Efs Qnr, a Potent DNA Gyrase Inhibitor
Author(s) -
Subray S. Hegde,
M.W. Vetting,
Lesley A. Mitchenall,
Anthony Maxwell,
John S. Blanchard
Publication year - 2011
Publication title -
antimicrobial agents and chemotherapy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.07
H-Index - 259
eISSN - 1070-6283
pISSN - 0066-4804
DOI - 10.1128/aac.01158-10
Subject(s) - dna gyrase , pentapeptide repeat , dna supercoil , biology , escherichia coli , novobiocin , microbiology and biotechnology , dna , biochemistry , bacteria , dna replication , genetics , peptide , gene
The chromosomally encoded Qnr homolog protein fromEnterococcus faecalis (Efs Qnr), when expressed, confers to its host a decreased susceptibility to quinolones and consists mainly of tandem repeats, which is consistent with belonging to the pentapeptide repeat family of proteins (PRPs).Efs Qnr was cloned with an N-terminal 6× His tag and purified to homogeneity.Efs Qnr partially protected DNA gyrase from fluoroquinolone inhibition at concentrations as low as 20 nM.Efs Qnr inhibited the ATP-dependent supercoiling activity of DNA gyrase with a 50% inhibitory concentration (IC50 ) of 1.2 μM, while no significant inhibition of ATP-independent relaxation activity was observed.Efs Qnr was cytotoxic when overexpressed inEscherichia coli , resulting in the clumping of cells and a loss of viability. The X-ray crystal structure ofEfs Qnr was determined to 1.6-Å resolution.Efs Qnr exhibits the right-handed quadrilateral beta-helical fold typical of PRPs, with features more analogous to MfpA (mycobacterium fluoroquinolone resistance pentapeptide) than to the PRPs commonly found in cyanobacteria.