Mine T, Morita Y, Kataoka A, Mizushima T, Tsuchiya T
Department of Microbiology, Faculty of Pharmaceutical Sciences, Okayama University, Tsushima, Okayama, 700-8530, Japan.
J Biochem. 1998 Jul;124(1):187-93. doi: 10.1093/oxfordjournals.jbchem.a022078.
We detected chloramphenicol/H+ antiport activity in membrane vesicles of Escherichia coli and cloned a gene for the antiporter from chromosomal DNA of E. coli. Introduction of the gene into E. coli cells conferred resistance to chloramphenicol and ethidium. A slight increase in resistance to acridine orange was also observed. Elevated chloramphenicol efflux and ethidium efflux were observed in cells harboring a plasmid carrying the gene. Addition of chloramphenicol to the assay mixture reduced the efflux of ethidium. Elevated chloramphenicol/H+ antiport activity was observed in membrane vesicles prepared from cells harboring the plasmid. The pH optimum for the activity was 6.5. We sequenced the gene and deduced the amino acid sequence of its product. A sequence homology search revealed that it was same as that of Cmr (or MdfA). Thus, it became clear that Cmr (MdfA) is the chloramphenicol(and ethidium)/H+ antiporter.
我们在大肠杆菌的膜囊泡中检测到氯霉素/H⁺反向转运活性，并从大肠杆菌的染色体DNA中克隆了该反向转运蛋白的基因。将该基因导入大肠杆菌细胞可使其对氯霉素和溴化乙锭产生抗性。还观察到对吖啶橙的抗性略有增加。在携带该基因的质粒的细胞中观察到氯霉素外排和溴化乙锭外排增加。向测定混合物中添加氯霉素可减少溴化乙锭的外排。在从携带该质粒的细胞制备的膜囊泡中观察到氯霉素/H⁺反向转运活性升高。该活性的最适pH为6.5。我们对该基因进行了测序，并推导了其产物的氨基酸序列。序列同源性搜索表明它与Cmr（或MdfA）相同。因此，很明显Cmr（MdfA）是氯霉素（和溴化乙锭）/H⁺反向转运蛋白。
