Kornberg H L, Lambourne L T
Department of Biochemistry, University of Cambridge, U.K.
Proc Biol Sci. 1992 Oct 22;250(1327):51-5. doi: 10.1098/rspb.1992.0129.
Mutants of Escherichia coli devoid of the membrane-spanning proteins PtsG and PtsMP, which are components of the phosphoenolpyruvate-dependent phosphotransferase system (PTS) and which normally effect the transport into the cells of glucose and mannose, do not grow upon or take up either sugar. Pseudorevertants are described that take up, and grow upon, mannose at rates strongly dependent on the mannose concentration in the medium (apparent Km > 5 mM); such mutants do not grow upon glucose but are derepressed for the components of the fructose operon. Evidence is presented that mannose is now taken up via the fructose-PTS to form mannose 6-phosphate, which is further utilized for growth via fructose 6-phosphate and fructose 1,6-bisphosphate.
缺乏跨膜蛋白PtsG和PtsMP的大肠杆菌突变体，这两种蛋白是磷酸烯醇丙酮酸依赖性磷酸转移酶系统（PTS）的组成部分，通常负责葡萄糖和甘露糖进入细胞的运输，它们在这两种糖上都不能生长或摄取。本文描述了一些假回复突变体，它们摄取甘露糖并在其上生长，其速率强烈依赖于培养基中的甘露糖浓度（表观Km>5 mM）；这些突变体在葡萄糖上不能生长，但对果糖操纵子的组分去阻遏。有证据表明，甘露糖现在通过果糖-PTS被摄取以形成6-磷酸甘露糖，后者通过6-磷酸果糖和1,6-二磷酸果糖进一步用于生长。
