Dataset Information

Isolation of cmr, a novel Escherichia coli chloramphenicol resistance gene encoding a putative efflux pump.

ABSTRACT: A novel gene designated cmr, which mapped to 18.8 min of the Escherichia coli K-12 genome, was shown to mediate resistance to chloramphenicol when it was expressed from a multicopy vector. The accumulation of chloramphenicol was significantly less in cells overexpressing cmr than in control cells harboring the vector without insert. After the addition of a proton motive force blocker, the level of accumulation of chloramphenicol in the resistant cells rapidly approached the levels found in sensitive cells carrying only the chromosomal cmr. Northern (RNA) blot analyses revealed that the cmr gene is expressed as a 1.3-kb transcript. This size corresponds very well with a predicted size of 1,293 nucleotides (nt) based on the mapping of the transcription initiation site to a G residue 24 nt upstream of the start codon and the presence of a putative rho-independent terminator sequence ending 36 nt downstream of the 1,233-nt open reading frame encoding the putative Cmr protein. The 411-residue-long derived amino acid sequence contains 12 putative transmembrane segments and displays significant sequence similarities to several known drug resistance protein sequences of the major facilitator family. We provide evidence strongly suggesting that the resistance mediated by Cmr involves active exclusion of chloramphenicol.

SUBMITTER: Nilsen IW

PROVIDER: S-EPMC178069 | biostudies-other | 1996 Jun

REPOSITORIES: biostudies-other

ACCESS DATA

Publications

Isolation of cmr, a novel Escherichia coli chloramphenicol resistance gene encoding a putative efflux pump.

Nilsen I W IW Bakke I I Vader A A Olsvik O O El-Gewely M R MR

Journal of bacteriology 19960601 11

A novel gene designated cmr, which mapped to 18.8 min of the Escherichia coli K-12 genome, was shown to mediate resistance to chloramphenicol when it was expressed from a multicopy vector. The accumulation of chloramphenicol was significantly less in cells overexpressing cmr than in control cells harboring the vector without insert. After the addition of a proton motive force blocker, the level of accumulation of chloramphenicol in the resistant cells rapidly approached the levels found in sensi ...[more]

PMID: 8655497

Similar Datasets

Project description:While antibiotic resistance poses a threat from both Gram-positive bacteria (GPB) and Gram-negative bacteria (GNB), GNB pose a more imminent public health hazard globally. GNB are a threat to growing antibiotic resistance because of the complex makeup of the membrane. The AcrAB-TolC efflux pump is a known resistance mechanism of Escherichia coli (E. coli) cells. This study utilized molecular dynamics modeling to visualize some of the changes occurring at a molecular level when airborne bacteria are exposed to stress and antibiotics. This study was conducted to build upon previous experimental research showing that there is an increase in antibiotic resistance and efflux pump activity when exposed to aerosolization. AcrB and AcrAB-TolC proteins were simulated under standard and increased pressure to compare the effect of aerosolization on the binding to the three different antibiotics (puromycin (PUY), ampicillin (AMP) and sulfamethoxazole-trimethoprim (SXT)) to the AcrB binding site. Analysis such as root-mean-square deviation of atomic positions and root-mean-square fluctuation, the opening of TolC, and the significant molecular mechanics with generalized Born and surface area solvation (MM-GBSA) scores associated with specific ligands were recorded. Resistance in experimental data indicated a relationship between the docking scores and some ligand-protein interactions. Results showed that there was more flexibility in the proteins within simulations conducted under standard pressure for the AcrB protein and the full tripartite complex AcrAB-TolC, showing that increased pressure causes more rigidity. MM-GBSA scores, used to calculate the free energy of ligand-protein binding, did not show a significant change, but interestingly, the strongest MM-GBSA scores were for ligands that moved to another binding pocket and did not result in resistance or opening of the efflux pump. However, the ligand moved from the binding site and did not cause the opening of TolC to increase significantly, whereas PUY and AMP were bound to the binding site for the duration of all simulations. AMP ligands under increased pressure showed the largest change in opening of the TolC efflux pump and aligns with experimental data showing E. coli cells had the most resistance to AMP after aerosolization. These results, in addition to other real-time changes such as OM proteins and mutations of targets within the cell, could be used to delineate and mitigate antibiotic resistance mechanisms.

Dataset Information

Isolation of cmr, a novel Escherichia coli chloramphenicol resistance gene encoding a putative efflux pump.

Publications

Isolation of cmr, a novel Escherichia coli chloramphenicol resistance gene encoding a putative efflux pump.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets