van der Vlag J, van Dam K, Postma P W
E. C. Slater Institute, University of Amsterdam, The Netherlands.
J Bacteriol. 1994 Jun;176(12):3518-26. doi: 10.1128/jb.176.12.3518-3526.1994.
The amount of IIAGlc, one of the proteins of the phosphoenolpyruvate:glucose phosphotransferase system (PTS), was modulated over a broad range with the help of inducible expression plasmids in Salmonella typhimurium. The in vivo effects of different levels of IIAGlc on glycerol and maltose metabolism were studied. The inhibition of glycerol uptake, by the addition of a PTS sugar, was sigmoidally related to the amount of IIAGlc. For complete inhibition of glycerol uptake, a minimal ratio of about 3.6 mol of IIAGlc to 1 mol of glycerol kinase (tetramer) was required. Varying the level of IIAGlc (from 0 to 1,000% of the wild-type level) did not affect the growth rate on glycerol, the rate of glycerol uptake, or the synthesis of glycerol kinase. In contrast, the growth rate on maltose, the rate of maltose uptake, and the synthesis of the maltose-binding protein increased two- to fivefold with increasing levels of IIAGlc. In the presence of cyclic AMP, the maximal levels were obtained at all IIAGlc concentrations. The synthesis of the MalK protein, the target of IIAGlc, was not affected by varying the levels of IIAGlc. The inhibition of maltose uptake was sigmoidally related to the amount of IIAGlc. For complete inhibition of maltose uptake by a PTS sugar, a ratio of about 18 mol of IIAGlc to 1 mol of MalK protein (taken as a dimer) was required.
葡萄糖磷酸转移酶系统（PTS）的一种蛋白质——IIAGlc的量，借助鼠伤寒沙门氏菌中的诱导表达质粒在很宽的范围内得到了调节。研究了不同水平的IIAGlc对甘油和麦芽糖代谢的体内效应。通过添加一种PTS糖对甘油摄取的抑制与IIAGlc的量呈S形相关。要完全抑制甘油摄取，需要IIAGlc与甘油激酶（四聚体）的摩尔比约为3.6∶1。改变IIAGlc的水平（从野生型水平的0到1000%）不会影响在甘油上的生长速率、甘油摄取速率或甘油激酶的合成。相反，随着IIAGlc水平的增加，在麦芽糖上的生长速率、麦芽糖摄取速率以及麦芽糖结合蛋白的合成增加了2至5倍。在存在环腺苷酸的情况下，在所有IIAGlc浓度下都能达到最大水平。IIAGlc的作用靶点——MalK蛋白的合成不受IIAGlc水平变化的影响。对麦芽糖摄取的抑制与IIAGlc的量呈S形相关。要通过一种PTS糖完全抑制麦芽糖摄取，需要IIAGlc与MalK蛋白（作为二聚体）的摩尔比约为18∶1。
