Stabb E V, Handelsman J
Department of Bacteriology, University of Wisconsin, Madison 53706, USA.
Mol Microbiol. 1998 Jan;27(2):311-22. doi: 10.1046/j.1365-2958.1998.00678.x.
Zwittermicin A is a novel aminopolyol antibiotic that represents a new structural class of antibiotic and has diverse biological activities, including the suppression of plant disease and the ability to inhibit prokaryotic and eukaryotic cells. To enhance our fundamental understanding and applications of zwittermicin A, we elucidated mechanisms of zwittermicin A resistance in Escherichia coli. Two classes of zwittermicin A-resistant mutants of E. coli were selected and characterized. One class included mutants altered in hemA, hemB, hemL, ubi, cydAB or atp, which were defective in generating a proton motive force (PMF) and resistant to aminoglycosides. The mutant analysis, coupled with physiological data, indicated an association between the electrical membrane potential (deltapsi) component of PMF and zwittermicin A sensitivity. A second class of zwittermicin A-resistant mutants was aminoglycoside sensitive and was affected in rpoB and rpoC, genes that encode subunits of RNA polymerase. The rpoB and rpoC mutants suggested that zwittermicin A might inhibit transcription, DNA replication, DNA gyrase or topoisomerase I; however, we found no further evidence to support any of these as the target for zwittermicin A. This study elucidated the genetic mechanisms of zwittermicin A resistance in E. coli. The results suggest that deltapsi drives zwittermicin A uptake, and that, unlike other antibiotics for which resistance maps in rpoB or rpoC, zwittermicin A does not cause the rapid cessation of DNA or RNA synthesis, suggesting a unique mechanism of antibiosis.
瑞斯托菌素A是一种新型氨基多元醇抗生素，代表了一类新的抗生素结构类别，具有多种生物活性，包括抑制植物病害以及抑制原核和真核细胞的能力。为了加强我们对瑞斯托菌素A的基本理解和应用，我们阐明了大肠杆菌中瑞斯托菌素A抗性的机制。我们选择并鉴定了两类对瑞斯托菌素A具有抗性的大肠杆菌突变体。一类包括在hemA、hemB、hemL、ubi、cydAB或atp中发生改变的突变体，这些突变体在产生质子动力（PMF）方面存在缺陷，并且对氨基糖苷类抗生素具有抗性。突变体分析与生理学数据相结合，表明PMF的电膜电位（deltapsi）成分与瑞斯托菌素A敏感性之间存在关联。第二类对瑞斯托菌素A具有抗性的突变体对氨基糖苷类抗生素敏感，并且在rpoB和rpoC中受到影响，这两个基因编码RNA聚合酶的亚基。rpoB和rpoC突变体表明瑞斯托菌素A可能抑制转录、DNA复制、DNA回旋酶或拓扑异构酶I；然而，我们没有找到进一步的证据来支持这些中的任何一个作为瑞斯托菌素A的靶标。这项研究阐明了大肠杆菌中瑞斯托菌素A抗性的遗传机制。结果表明，deltapsi驱动瑞斯托菌素A的摄取，并且与rpoB或rpoC中存在抗性图谱的其他抗生素不同，瑞斯托菌素A不会导致DNA或RNA合成的快速停止，这表明了一种独特的抗菌机制。
