Summary: Washed cells of prepared from a fructose-limited continuous culture (D 0.045 h) transported D-[UC]fructose in a linear manner for up to 4 min at a rate several-fold higher than the rate of fructose utilization by the growing culture. D-[UC]Fructose transport exhibited a high affinity for fructose ( < 1 μM) and was inhibited to varying extents by osmotic shock, by the uncoupling agent carbonyl cyanide , and by unlabelled sugars (D-fructose/D-mannose > D-ribose > D-sorbose > D-glucose/D-galactose/D-xylose; no inhibition by D-arabinose). Prolonged growth of in fructose-limited continuous culture led to the selection of a novel strain (AR100) which overproduced a fructose-binding protein (FBP) and showed an increased rate of fructose transport. FBP was purified from osmotic-shock fluid using anion-exchange fast protein liquid chromatography (FPLC). The monomeric protein (M 34200 by SDS-PAGE and 37700 by gel-filtration FPLC) bound D-[UC]-fructose stoichiometrically (1.17 nmol nmol FBP) and with high affinity (K 0.49 μM) as shown by equilibrium dialysis. Binding of D-[UC]fructose by FBP was variably inhibited by unlabelled sugars (D-fructose/D-mannose > D-ribose > D-sorbose; no inhibition by D-glucose, D-galactose or D-arabinose). The N-terminal amino acid sequence of FBP (ADTSVCLI-) was similar to that of several sugar-binding proteins from other species of bacteria. Fructose transport and FBP were variably induced in batch cultures of by growth on different carbon sources (D-fructose > D-ribose/D-mannose > D-glucose; no induction by succinate). An immunologically similar protein to FBP was produced by and various species of following growth on fructose. It is concluded that fructose is transported into and related organisms via a periplasmic fructose/mannose-binding-protein-dependent active-transport system, in contrast to the phosphotransferase system used by many other species of bacteria.


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