Melibiose‐Cation Cotransport System of Escherichia coli a
Melibiose‐Cation Cotransport System of Escherichia coli a
复制标题
大肠杆菌的蜜二糖-阳离子共转运系统
DOI：
10.1111/j.1749-6632.1985.tb14884.x
复制
发表时间：
1985
影响因子：
5.2
通讯作者：
T. Wilson
中科院分区：
文献类型：
--
作者：
T. Tsuchiya;Dorothea M. Wilson;T. Wilson
A common mechanism for nutrient uptake by cells is cation-substrate cotransport. Representatives of this class of membrane carrier are found in all prokaryotic and eukaryotic cells that have been examined.' In bacteria the cation used for many such processes is the proton, while in animal cells it is exclusively the sodium ion that is used for cotransport. The melibiose carrier of Escherichia coli is unusual in its ability to use either H+ or Na+.' This is of interest from an evolutionary point of view since it may be considered an intermediate stage in the evolution from a proton cotransport system to that of Na+ (FIG. 1). The melibiose carrier of E . coli was discovered by Prestidge and Pardee in 1965.' Stock and Roseman4 then showed that the analogous carrier of Salmonella typhimurium functions with Na+ cotransport. This observation was subsequently confirmed and further studied in membrane vesicles of S. typhimurium.5*6 Cotransport with N a + was later demonstrated for the melibiose carrier of E . coli.' It therefore came as a surprise to find that melibiose addition to anaerobic cells of E. coli caused proton uptake' (suggesting H+-melibiose cotransport). A variety of explanations for these observations was explored,' including the possibility of a second carrier for melibiose and all proved inconsistent with the data. It now seems that the carrier recognizes H+ in addition to Na' and Li+ with different cation specificities for different substrates. Recent studies have given additional support for the view that the melibiose carrier can recognize several cations. Experiments have been carried out to show competitive inhibition between different cations for cotransport. Furthermore, mutants have been isolated with altered specificity for more than one cation. A significant advance has been the cloning and sequencing of the DNA for the melibiose transport geneg and the subsequent sequencing of the mutant W3133-28 for comparison.''
