Membrane translocation of mannitol in Escherichia coli without phosphorylation

Galactosyl-mannitol can be transported into cells of Escherichia coli by beta-galactoside permease and can be hydrolyzed rapidly to mannitol and galactose by beta-galactosidase. When a mutant strain lacking enzyme I of the phosphoenolpyruvate phosphotransferase system and constitutive in the lactose system was presented with galactosyl-mannitol in which the mannitol moiety was labeled with (3)H, the liberated mannitol remained inside the cell if the Enzyme II complex of the phosphoenolpyruvate phosphotransferase system for mannitol was uninduced. It is postualted that one of the enzyme II proteins can still catalyze translocation of mannitol across the cell membrane even when phsophorylation is not possible.