Anderson Todd, Brian Paul, Riggle Perry, Kong Renqiu, Champness Wendy
Department of Microbiology, Michigan State University, East Lansing, MI 48824-1101, USA1.
Microbiology (Reading). 1999 Sep;145 ( Pt 9):2343-2353. doi: 10.1099/00221287-145-9-2343.
The absA locus in Streptomyces coelicolor A3(2) was identified because mutations in it uncoupled sporulation from antibiotic synthesis: absA mutants failed to produce any of the four antibiotics characteristic of S. coelicolor. These mutants are now shown to contain point mutations in the absA1 gene which encodes the histidine kinase sensor-transmitter protein of a two-component signalling system. The absA1 non-antibiotic-producing mutants, which are unpigmented, spontaneously acquire pigmented colony sectors. Genetic analysis established that the pigmented sectors contain second-site suppressive mutations, sab (for suppressor of abs). Phenotypic characterization showed that sab strains produce all four antibiotics; some overproduce antibiotics and are designated Pha, for precocious hyperproduction of antibiotics. A set of sab mutations responsible for suppression was localized by plasmid-mediated and protoplast fusion mapping techniques to the vicinity of the absA locus. DNA cloned from this region was used to construct phage that could transduce sab mutations. Sequence analysis of sab strains defined sab mutations in both the absA1 gene and the absA2 gene; the latter encodes the two-component system's response regulator.
天蓝色链霉菌A3(2)中的absA位点被鉴定出来，是因为其中的突变使孢子形成与抗生素合成解偶联：absA突变体无法产生天蓝色链霉菌特有的四种抗生素中的任何一种。现在发现这些突变体在absA1基因中含有点突变，该基因编码双组分信号系统的组氨酸激酶传感-传递蛋白。不产生抗生素的absA1突变体没有色素，会自发获得有色菌落区域。遗传分析表明，有色区域含有第二位点抑制突变，即sab（abs的抑制子）。表型特征表明，sab菌株能产生所有四种抗生素；有些菌株抗生素过量产生，被称为Pha，即抗生素早熟过量产生。通过质粒介导和原生质体融合定位技术，将一组负责抑制作用的sab突变定位到absA位点附近。从该区域克隆的DNA被用于构建能够转导sab突变的噬菌体。对sab菌株的序列分析确定了absA1基因和absA2基因中的sab突变；后者编码双组分系统的应答调节因子。
