Hotta K, Ishikawa J, Ogata T, Mizuno S
Department of Antibiotics, National Institute of Health, Tokyo, Japan.
Gene. 1992 Jun 15;115(1-2):113-7. doi: 10.1016/0378-1119(92)90548-4.
The role of aminoglycoside (AG) acetyltransferases (AACs) and of the corresponding genes in resistance to foreign AGs in AG-producing strains of Streptomyces were studied. The research focussed on (i) the activation mechanism of the cryptic kanamycin(Km)-resistance-encoding gene that encodes an AAC(3) in streptomycin-producing S. griseus SS-1198, and (ii) an AAC(2') with novel activity and substrate specificity in kasugamycin-producing S. kasugaensis MB273. Activation of the cryptic kan gene in S. griseus SS-1198 is probably due to a single base substitution at the putative -10 promoter region, leading to the enhancement of transcription, resulting in resistance to AG. The coding region of the kan gene was highly homologous to that of the aacC7 gene of paromomycin-producing S. rimosus forma paromomycinus. On the other hand, resistance in S. kasugaensis MB273 was found to be due to an AAC(2') capable of acetylating astromicin group AGs at two different sites (1-NH2 with istamycin B, and 2'-NH2 with astromicin and istamycin A). These additional antibiotic resistances that are independent of a self-resistance basis may be regarded as 'secondary' resistances, so as to distinguish them from 'primary' resistances arising from a self-resistance basis.
研究了氨基糖苷类（AG）乙酰转移酶（AACs）及其相应基因在链霉菌AG产生菌株对外源AG耐药性中的作用。该研究聚焦于：（i）在链霉素产生菌灰色链霉菌SS-1198中，编码AAC(3)的隐性卡那霉素（Km）抗性编码基因的激活机制；（ii）在春日霉素产生菌春日链霉菌MB273中具有新活性和底物特异性的AAC(2')。灰色链霉菌SS-1198中隐性卡那基因的激活可能是由于假定的-10启动子区域的单个碱基替换，导致转录增强，从而产生对AG的抗性。卡那基因的编码区与巴龙霉素产生菌龟裂链霉菌巴龙霉素变种的aacC7基因高度同源。另一方面，发现春日链霉菌MB273中的抗性是由于一种AAC(2')，它能够在两个不同位点乙酰化阿司米星类AGs（与异他霉素B的1-NH2位点，以及与阿司米星和异他霉素A的2'-NH2位点）。这些独立于自身抗性基础的额外抗生素抗性可被视为“二级”抗性，以便将它们与源于自身抗性基础的“一级”抗性区分开来。
