Inoue C, Sugawara K, Kusano T
Biotechnology Institute, Akita Prefectural College of Agriculture, Japan.
Gene. 1990 Nov 30;96(1):115-20. doi: 10.1016/0378-1119(90)90349-v.
The merA upstream nucleotide (nt) sequence (1378 bp) of the Hg2(+)-resistance-encoding gene system (mer) in Thiobacillus ferrooxidans, was determined. The region contains two open reading frames: unidentified reading frame 1 (URF1) and merC. URF1 has 63-73% homology with those of Tn501, R100 and pDU1358, although the corresponding product has not yet been identified. Thiobacillus merC had 61% and 55% homology with R100 merC at the nt and amino acid (aa) sequence levels, respectively, and its product, consisting of 143 aa, was highly hydrophobic. No sequence homologous to merR, merT. merP or merD of R100 were observed on either strand. Within the 70-100-bp sequence upstream from the merC start codon. there was a sequence highly homologous to the promoter of merT of other Gram- mer systems. From primer extension and Northern-blot analyses, it became clear that merC and merA were co-transcribed from this putative transcription start point. The mer transcript in T. ferrooxidans was only detected in Hg2(+)-induced cells. Therefore, it was concluded that the T. ferrooxidans mer system is an inducible operon.
测定了氧化亚铁硫杆菌中汞离子抗性编码基因系统（mer）的merA上游核苷酸（nt）序列（1378 bp）。该区域包含两个开放阅读框：未鉴定阅读框1（URF1）和merC。URF1与Tn501、R100和pDU1358的URF1具有63 - 73%的同源性，尽管相应产物尚未鉴定。氧化亚铁硫杆菌的merC在核苷酸和氨基酸序列水平上与R100的merC分别具有61%和55%的同源性，其产物由143个氨基酸组成，具有高度疏水性。在两条链上均未观察到与R100的merR、merT、merP或merD同源的序列。在merC起始密码子上游70 - 100 bp的序列内，存在一个与其他革兰氏阴性菌mer系统的merT启动子高度同源的序列。通过引物延伸和Northern印迹分析表明，merC和merA从这个假定的转录起始点共同转录。氧化亚铁硫杆菌中的mer转录本仅在汞离子诱导的细胞中检测到。因此，得出结论，氧化亚铁硫杆菌的mer系统是一个可诱导操纵子。
