August P R, Rahn J A, Flickinger M C, Sherman D H
Department of Microbiology, University of Minnesota, St. Paul 55108, USA.
Gene. 1996 Oct 10;175(1-2):261-7. doi: 10.1016/0378-1119(96)00172-2.
The mcr locus from Streptomyces lavendulae confers high level resistance (> 100 micrograms/ml) to mitomycin C (MC) and related mitomycins when cloned into Streptomyces lividans. Production of the mcrA gene product (MCRA) was shown to be MC-inducible by identification of MCRA (M(r) of 54 kDa) using Western blot analysis and enzyme linked immunosorbent assay (ELISA). The magnitude of MCRA production was dependent on MC concentration, with primary induction starting at 0.1 microgram/ml and maximum induction at 10 micrograms/ml of the drug. Different levels of MCRA production were observed when other mitomycin metabolites were used as inducers, and the level of induction related directly to aziridine ring substitution on the individual molecules. Moreover, inducible synthesis of the mcr A gene product was unique to this structural class since production of MCRA did not occur as a general response to DNA damaging agents. The time profile of intracellular MCRA synthesis correlated with MC production in S. lavendulae, suggesting coordinated regulation of MC resistance and biosynthetic genes.
当来自淡紫色链霉菌的mcr基因座克隆到变铅青链霉菌中时，可赋予对丝裂霉素C（MC）及相关丝裂霉素的高水平抗性（>100微克/毫升）。通过蛋白质免疫印迹分析和酶联免疫吸附测定（ELISA）鉴定出M(r)为54 kDa的MCRA，结果表明mcrA基因产物（MCRA）的产生是由MC诱导的。MCRA产生的量取决于MC的浓度，初次诱导从药物浓度为0.1微克/毫升开始，在10微克/毫升时达到最大诱导。当使用其他丝裂霉素代谢产物作为诱导剂时，观察到不同水平的MCRA产生，并且诱导水平与各个分子上的氮丙啶环取代直接相关。此外，mcr A基因产物的可诱导合成是该结构类所特有的，因为MCRA的产生不是对DNA损伤剂的普遍反应。细胞内MCRA合成的时间曲线与淡紫色链霉菌中MC的产生相关，表明MC抗性和生物合成基因受到协同调控。
