Related Experiment Video
Updated: Jul 6, 2026

Antimicrobial Peptides Produced by Selective Pressure Incorporation of Non-canonical Amino Acids
Published on: May 4, 2018
Qnr-like pentapeptide repeat proteins in gram-positive bacteria
J M Rodríguez-Martínez1, C Velasco, A Briales
1Department of Microbiology, University of Seville, Seville, Spain. jmrodriguez@us.es
Objectives:
To study the role of Qnr-like pentapeptide repeat proteins (PRPs) from several gram-positive species with quinolone resistance in vitro.
Methods:
A PCR-based strategy was used to clone and express genes coding for Qnr-like PRPs in Enterococcus faecalis, Enterococcus faecium, Listeria monocytogenes, Clostridium perfringens, C. difficile, Bacillus cereus and B. subtilis in Escherichia coli DH10B. MIC values of nalidixic acid and fluoroquinolones were determined for reference strains and E. coli DH10B harbouring recombinant plasmids containing genes coding for PRPs.
Results:
Amino acid identity of Qnr-like PRPs in gram-positive strains compared with that of the plasmid-mediated quinolone resistance determinants QnrA1, QnrB1 and QnrS1 was in the range of 16% to 22%. Recombinant plasmids coding for Qnr-like PRPs conferred reduced susceptibility to fluoroquinolones (in the range of 0.016 to 0.064 mg/L for ciprofloxacin) and nalidixic acid (from 6 to 12 mg/L), depending on the antimicrobial agent and PRP. The PRP from B. subtilis showed no protective effect.
Conclusions:
The PRPs analysed conferred a reduced susceptibility phenotype in E. coli; the data provide further evidence of the possible roles in quinolone resistance of PRPs from different gram-positive species. These gram-positive species may constitute a reservoir for Qnr-like quinolone resistance proteins.
Related Concept Videos
Bacterial RNA Polymerase
In most genes, the transcription site is a single base present upstream of the coding sequence. Though RNAP is a catalytically efficient enzyme, it does not recognize...
Peptidoglycan Synthesis
Cytoskeletal Proteins in Bacteria
Gene Regulation in Microbial Communities: Quorum Sensing
Types of RNA
Three main types of RNA are involved in protein synthesis: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). These RNAs perform diverse functions and can be broadly classified as protein-coding or non-coding RNA. Non-coding RNAs play important roles in the regulation of gene expression in response to developmental and environmental changes. Non-coding RNAs in prokaryotes can be manipulated to develop more effective antibacterial drugs for human or animal use.
RNA...
Nucleoid

