QnrS1 structure-activity relationships.

ABSTRACT:

Objectives

Loop B is important for low-level quinolone resistance conferred by Qnr proteins. The role of individual amino acids within QnrS1 loop B in quinolone resistance and gyrase protection was assessed.

Methods

qnrS1 and 11 qnrS1 alleles with site-directed Ala mutations in loop B were expressed in Escherichia coli BL21(DE3) and proteins were purified by affinity chromatography. Ciprofloxacin MICs were determined with and without IPTG. Gyrase DNA supercoiling was measured with and without ciprofloxacin IC50 and with various concentrations of QnrS1 proteins.

Results

Wild-type QnrS1 and QnrS1 with Asn-110→Ala and Arg-111→Ala substitutions increased the ciprofloxacin MIC 12-fold in BL21(DE3), although QnrS1 with Gln-107→Ala replacement increased it 2-fold more than w

SUBMITTER: Tavio MM 

PROVIDER: S-EPMC4100707 | biostudies-literature | 2014 Aug

REPOSITORIES: biostudies-literature