Defective enzyme II-BGlc of the phosphoenolpyruvate:sugar phosphotransferase system leading to uncoupling of transport and phosphorylation in Salmonella typhimurium.

摘要: Transport and phosphorylation of glucose via enzymes II-A/II-B II-BGlc the phosphoenolpyruvate:sugar phosphotransferase system are tightly coupled in Salmonella typhimurium. Mutant strains (pts) that lack phosphorylating proteins this system, enzyme I HPr, unable to transport or grow on glucose. From ptsHI deletion S. typhimurium, mutants were isolated regained growth Several lines evidence suggest these Glc+ have an altered as follows. (i) Insertion a ptsG::Tn10 mutation (resulting defective II-BGlc) abolished strains. Introduction ptsM mutation, other hand, which abolishes activity, had no effect. (ii) Methyl alpha-glucoside (specific for was lowered absent ptsH+,I+ transductants phosphoenolpyurate:sugar sugars normal. (iii) Membranes from catalyze transphosphorylation methyl by 6-phosphate, but mannose 6-phosphate (iv) The ptsG gene closely linked it. We conclude has acquired capacity absence system-mediated phosphorylation. However, affinity decreased at least 1,000-fold compared wild-type strain. At same time mutated lost ability its substrates IIIGlc.