Sugar transporters from bacteria, parasites and mammals: structure-activity relationships

Sugar transport across the plasma membrane is one of the most important tra nsport processes. The cloning and expression of cDNAs from a superfamily of related sugar transporters that all adopt a 12-membrane-spanning-domain st ructure has opened new avenues of investigation, including pre steady-state kinetic analysis. Structure-function analyses of mammalian and bacterial s ugar transporters, and comparisons of these transporters with those of para sitic trypanosomatids, indicate that different environmental pressures have tailored the evolution of the various members of the sugar-transporter sup erfamily. Subtle distinctions in the function of these proteins can be rela ted to particular amino acid residue substitutions.