Binding of the substrate analogue perseitol to phosphorylated and unphosphorylated enzyme IImtl of the phosphoenolpyruvate-dependent phosphotransferase system of Escherichia coli.
Enzyme IImtl catalyzes the concomitant transport and phosphorylation of the hexitol mannitol. Here we demonstrate that the heptitol perseitol is not phosphorylated and not transported by the enzyme. However, the enzyme binds perseitol with an affinity comparable to the affinity for mannitol. Apparent affinities of the phosphorylated enzyme for perseitol were inferred from the inhibition by perseitol of mannitol phosphorylation and uptake. Apparent affinities of the unphosphorylated enzyme follow from the inhibition of mannitol binding to the enzyme. Mechanistic interpretations of the apparent inhibition constants are discussed, and it is concluded that phosphorylation of the cytoplasmic domain of enzyme IImtl has little effect on the affinity of the membrane-bound domain of the enzyme for perseitol.
Department of Biochemistry, University of Groningen, The Netherlands.
J S
JS
Lolkema
E S
ES
Wartna
G T
GT
Robillard
D001667:Binding, Competitive; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology*; D029968:Escherichia coli Proteins; D006539:Heptoses / Q000378:metabolism* / Q000494:pharmacology; D007700:Kinetics; D008353:Mannitol / Q000378:metabolism; D009004:Monosaccharide Transport Proteins; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010766:Phosphorylation
D029968:Escherichia coli Proteins; D006539:Heptoses; D009004:Monosaccharide Transport Proteins; D008353:Mannitol; C025642:perseitol; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C022358:mannitol PTS permease, E coli