Kato Jun-ya, Suzuki Ayano, Yamazaki Haruka, Ohnishi Yasuo, Horinouchi Sueharu
Department of Biotechnology, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Japan.
J Bacteriol. 2002 Nov;184(21):6016-25. doi: 10.1128/JB.184.21.6016-6025.2002.
In Streptomyces griseus, A-factor (2-isocapryloyl-3R-hydroxymethyl-gamma-butyrolactone) switches on aerial mycelium formation and secondary metabolite biosynthesis. An A-factor-dependent transcriptional activator, AdpA, activates multiple genes required for morphological development and secondary metabolism in a programmed manner. A region upstream of a zinc-containing metalloendopeptidase gene (sgmA) was found among the DNA fragments that had been isolated as AdpA-binding sites. The primary product of sgmA consisted of N-terminal pre, N-terminal pro, mature, and C-terminal pro regions. sgmA was transcribed in an AdpA-dependent manner, and its transcription was markedly enhanced at the timing of aerial mycelium formation. AdpA bound two sites in the region upstream of the sgmA promoter; one was at about nucleotide position -60 (A site) with respect to the transcriptional start point of sgmA, and the other was at about position -260 (B site), as determined by DNase I footprinting. Transcriptional analysis with mutated promoters showed that the A site was essential for the switching on of sgmA transcription and that the B site was necessary for the marked enhancement of transcription at the timing of aerial mycelium formation. Disruption of the chromosomal sgmA gene resulted in a delay in aerial hypha formation by half a day. SgmA is therefore suggested to be associated with the programmed morphological development of Streptomyces, in which this peptidase, perhaps together with other hydrolytic enzymes, plays a role in the degradation of proteins in substrate hyphae for reuse in aerial hypha formation.
在灰色链霉菌中，A因子（2-异辛酰基-3R-羟甲基-γ-丁内酯）开启气生菌丝体的形成和次级代谢产物的生物合成。一种依赖A因子的转录激活因子AdpA，以程序化的方式激活形态发育和次级代谢所需的多个基因。在作为AdpA结合位点分离出的DNA片段中，发现了一个含锌金属内肽酶基因（sgmA）上游的区域。sgmA的初级产物由N端前导区、N端前肽区、成熟区和C端前肽区组成。sgmA以依赖AdpA的方式转录，其转录在气生菌丝体形成时显著增强。AdpA结合在sgmA启动子上游区域的两个位点；通过DNA酶I足迹法确定，一个位点相对于sgmA转录起始点约在核苷酸位置-60（A位点），另一个位点约在位置-260（B位点）。对突变启动子的转录分析表明，A位点对于sgmA转录的开启至关重要，而B位点对于气生菌丝体形成时转录的显著增强是必需的。染色体sgmA基因的破坏导致气生菌丝形成延迟半天。因此，推测SgmA与链霉菌的程序化形态发育有关，在这种发育过程中，这种肽酶可能与其他水解酶一起，在降解基质菌丝中的蛋白质以用于气生菌丝形成的再利用中发挥作用。
