Role of MerT and MerP from Pseudomonas K-62 plasmid pMR26 in the transport of phenylmercury.
Role of MerT and MerP from Pseudomonas K-62 plasmid pMR26 in the transport of phenylmercury.
复制标题
假单胞菌 K-62 质粒 pMR26 中 MerT 和 MerP 在苯汞转运中的作用。
DOI：
10.1248/bpb.23.279
复制
发表时间：
2000
影响因子：
2
通讯作者：
H. Pan‐Hou
中科院分区：
文献类型：
--
作者：
M. Kiyono;Y. Uno;T. Omura;H. Pan‐Hou
为了研究假单胞菌K-62 pMR 26编码的MerT和MerP在苯汞转运中的作用，构建了一系列merT点突变和/或merP基因缺失的突变体，并转化大肠杆菌XL 1-Blue。苯汞在大肠杆菌细胞质膜上的转运。NaCN和低温均能抑制MerT和MerP介导的大肠杆菌表达。merP的缺失降低了C6 H5 Hg+的超摄取和超敏感表型，但没有完全消除，这表明苯汞进入细胞质的转运。大肠杆菌仍然存在。在MerT的第一跨膜区的邻位半胱氨酸残基（Cys 24和Cys 25）突变为丝氨酸引起的汞2 +-超摄取和超敏性的完全丧失，而突变不影响C6 H5汞+-超摄取和超敏表型。此外，没有添加剂对C6 H5 Hg+的超吸收和超敏表型的影响被发现，当突变的两个半胱氨酸在MerT丝氨酸进一步引入merP缺失突变体。这些结果清楚地表明，邻近的半胱氨酸残基的MerT不参与运输的C6 H5 Hg+，但确实参与运输的Hg 2+，如以前报道的。
To investigate the individual role of MerT and MerP encoded by Pseudomonas K-62 pMR26 in the transport of phenylmercury, a series of mutants with a specific point mutation in merT and/or genetic deletion in merP were constructed and transformed into Escherichia coli XL1-Blue. Transport of phenylmercury across the cytoplasmic membrane of E. coli mediated by MerT and MerP was inhibited by NaCN and by cold temperatures. Deletion of merP reduced, but did not completely abolish the C6H5Hg+-hyperuptake and -hypersensitive phenotypes suggesting that transport of phenylmercury into the cytoplasm of E. coli is still occurring. Mutations of the vicinal cysteine residues (Cys24 and Cys25) in the first transmembrane region of MerT to serine caused complete loss of Hg2+-hyperuptake and -hypersensitivity, whereas the mutations did not affect the C6H5Hg+-hyperuptake and -hypersensitive phenotypes. In addition, no additive effect on the C6H5Hg+-hyperuptake and -hypersensitive phenotypes was found, when mutations of the two cysteines in MerT to serine were further introduced in the merP-deleted mutants. These results clearly demonstrated that the vicinal cysteine residues of MerT are not involved in the transport of C6H5Hg+, but indeed are involved in the transport of Hg2+ as previously reported.