Energization of the transport systems for arabinose and comparison with galactose transport in Escherichia coli

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Abstract
Strains of E. coli were obtained containing either the AraE or the AraF transport system for arabinose. AraE+,AraF- strains effected energized accumulation and displayed an arabinose-evoked alkaline pH change indicative of arabinose-H+ symport. In contrast, AraE-, AraF+ strains accumulated arabinose but did not display H+ symport. The ability of different sugars and their derivatives to elicit sugar-H+ symport in AraE+ strains was examined. Only L-arabinose and D- fucose were good substrates, and arabinose was the only inducer. Membrane vesicles prepared from an AraE+, AraF+ strain accumulated the sugar, energized most efficiently by the respiratory substrates ascorbate and phenazine methosulfate. Addition of arabinose or fucose to an anaerobic suspension of membrane vesicles caused an alkaline pH change indicative of sugar-H+ symport on the membrane-bound transport system. Kinetic studies and the effects of arsenate and uncoupling agents in intact cells and membrane vesicles gave further evidence that AraE is a low-affinity membrane-bound sugar-H+ symport system and that AraF is a binding-protein-dependent high-affinity system that does not require a transmembrane proton motive force for energization. Arabinose transport into E. coli is energized by an electrochemical gradient of protons (AraE system) or by phosphate bond energy (AraF system). In batch cultures the rates of growth and carbon cell yields on arabinose were lower in AraE-, AraF+ strains than in AraE+, AraF- or AraE+, AraF+ strains. The AraF system was more susceptible to catabolite repression than was the.