Csonka L N
Basic Life Sci. 1981;18:533-42. doi: 10.1007/978-1-4684-3980-9_32.
Previously we demonstrated that high intracellular proline levels conferred enhanced osmotolerance on Salmonella typhimurium. Stimulation of growth rate under conditions of osmotic inhibition could be brought about either by the addition of proline to the culture media or by mutations which result in proline over-production. Here, we report that there is a novel proline transport system in S. typhimurium which is activated in media of elevated osmolarity. this conclusion is based on the observation that putP- proP- double mutants, which lack both of the known proline permeases are resistant in minimal medium to the toxic proline analogues 3,4-dehydro-D, L-proline and L-azetidine-2-carboxylate. However, they regain sensitivity to the analogues in media of elevated osmolarity. Selecting resistance to 3,4-dehydro-D, L-proline in media of elevated osmolarity, we obtained mutants of putP- proP- strains which lack the osmotically activated proline permease. In these strains, exogenous proline could no longer alleviate osmotic inhibition.
此前我们证明，细胞内高脯氨酸水平赋予鼠伤寒沙门氏菌增强的渗透压耐受性。在渗透压抑制条件下，通过向培养基中添加脯氨酸或通过导致脯氨酸过量产生的突变，均可提高生长速率。在此，我们报道鼠伤寒沙门氏菌中存在一种新型脯氨酸转运系统，该系统在高渗培养基中被激活。这一结论基于以下观察结果：putP- proP-双突变体缺乏两种已知的脯氨酸通透酶，在基本培养基中对有毒的脯氨酸类似物3,4-脱氢-D，L-脯氨酸和L-氮杂环丁烷-2-羧酸具有抗性。然而，它们在高渗培养基中对这些类似物重新变得敏感。在高渗培养基中选择对3,4-脱氢-D，L-脯氨酸的抗性，我们获得了putP- proP-菌株的突变体，这些突变体缺乏渗透激活的脯氨酸通透酶。在这些菌株中，外源脯氨酸不再能减轻渗透压抑制。
