The identification of a new family of sugar efflux pumps in Escherichia coli

Using a functional cloning strategy with an Escherichia coli genomic plasmi d library, we have identified a new family of sugar efflux proteins with th ree highly homologous members in the E. coli genome, In addition, two open reading frames, one present in Yersinia pestis and the other in Deinococcus radiodurans, appear to encode closely related proteins. An in vitro transp ort assay using inside-out membrane vesicles prepared from overproducing st rains was used to demonstrate that members of this new family can efflux [C -14]-lactose. As sugar efflux phenomena have been reported previously in se veral bacterial species including E. coli, the identification of a new fami ly of sugar efflux proteins may help to reveal the physiological role of su gar efflux in metabolism. It is proposed that the E. coli members of this f amily, whose functions were previously unknown, be given the gene family de signation SET for sugar efflux transporter.