Klyachko K A, Neyfakh A A
Center for Pharmaceutical Biotechnology and Department of Medicinal Chemistry and Pharmacognosy, University of Illinois, Chicago, Illinois 60607, USA.
J Bacteriol. 1998 Jun;180(11):2817-21. doi: 10.1128/JB.180.11.2817-2821.1998.
Substitution of threonine or serine for the evolutionary conserved intramembrane proline P347 of the Bacillus subtilis multidrug transporter Bmr significantly increases the toxin-effluxing activity of Bmr without affecting its abundance in the cell. In cocultivation experiments, we demonstrate that although the mutant T347 Bmr is advantageous to cells growing in the presence of a toxin, the wild-type P347 Bmr is advantageous under the conditions of nutritional limitation. This may explain why Bmr has evolved the way it did, that is, with proline at position 347. These observations provide a basis for speculating that the evolution of Bmr has been determined by its presently unidentified natural function rather than by its ability to expel diverse toxins from the cell.
将苏氨酸或丝氨酸取代枯草芽孢杆菌多药转运蛋白Bmr进化保守的膜内脯氨酸P347，可显著提高Bmr的毒素外排活性，而不影响其在细胞中的丰度。在共培养实验中，我们证明，虽然突变体T347 Bmr对在毒素存在下生长的细胞有利，但野生型P347 Bmr在营养限制条件下更具优势。这或许可以解释Bmr为何会以目前的方式进化，即在347位含有脯氨酸。这些观察结果为推测Bmr的进化是由其目前尚未明确的天然功能而非从细胞中排出多种毒素的能力所决定提供了依据。
