Hao Z, Chen S, Wilson D B
Institute for Comparative and Environmental Toxicology, Cornell University, Ithaca, New York 14853, USA.
Appl Environ Microbiol. 1999 Nov;65(11):4746-52. doi: 10.1128/AEM.65.11.4746-4752.1999.
An Mn(2+) and Cd(2+) uptake gene, mntA, was cloned from Lactobacillus plantarum ATCC 14917 into Escherichia coli. Its expression conferred on E. coli cells increased Cd(2+) sensitivity as well as energy-dependent Cd(2+) uptake activity. Both transcription and translation of mntA were induced by Mn(2+) starvation in L. plantarum, as indicated by reverse transcriptase PCR and immunoblotting. Two Cd(2+) uptake systems have been identified in L. plantarum: one is a high-affinity Mn(2+) and Cd(2+) uptake system that is expressed in Mn(2+)-starved cells, and the other is a nonsaturable Cd(2+) uptake system that is expressed in Cd(2+)-sufficient cells (Z. Hao, H. R. Reiske, and D. B. Wilson, Appl. Environ. Microbiol. 65:592-99, 1999). MntA was not detected in an Mn(2+)-dependent mutant of L. plantarum which had lost high-affinity Mn(2+) and Cd(2+) uptake activity. The results suggest that mntA is the gene encoding the high-affinity Mn(2+) and Cd(2+) transporter. On the basis of its predicted amino acid sequence, MntA belongs to the family of P-type cation-translocating ATPases. The topology and potential Mn(2+)- and Cd(2+)-binding sites of MntA are discussed. A second clone containing a low-affinity Cd(2+) transport system was also isolated.
从植物乳杆菌ATCC 14917中克隆出一个锰离子（Mn(2+)）和镉离子（Cd(2+)）摄取基因mntA，并将其导入大肠杆菌。该基因的表达使大肠杆菌细胞对Cd(2+)的敏感性增加，同时赋予其能量依赖性的Cd(2+)摄取活性。逆转录聚合酶链反应（RT-PCR）和免疫印迹结果表明，在植物乳杆菌中，mntA的转录和翻译均受Mn(2+)饥饿诱导。在植物乳杆菌中已鉴定出两种Cd(2+)摄取系统：一种是在Mn(2+)饥饿细胞中表达的高亲和力Mn(2+)和Cd(2+)摄取系统，另一种是在Cd(2+)充足细胞中表达的非饱和性Cd(2+)摄取系统（Z. Hao、H. R. Reiske和D. B. Wilson，《应用与环境微生物学》65:592 - 99，1999年）。在植物乳杆菌的一个Mn(2+)依赖性突变体中未检测到MntA，该突变体已丧失高亲和力Mn(2+)和Cd(2+)摄取活性。结果表明，mntA是编码高亲和力Mn(2+)和Cd(2+)转运蛋白的基因。根据其预测的氨基酸序列，MntA属于P型阳离子转运ATP酶家族。文中还讨论了MntA的拓扑结构以及潜在的Mn(2+)和Cd(2+)结合位点。此外，还分离出了一个包含低亲和力Cd(2+)转运系统的第二个克隆。
