Cell envelope proteins involved in the transport of maltose and sn-glycerol-3-phosphate in Escherichia coli.

Two types of proteins are discussed in their role of facilitating the transport of maltose and sn-glycerol-3-phosphate in E. coli. The first protein is the receptor for phage lambda, known to be an outer membrane protein. By facilitating the diffusion of maltose and the higher maltodextrins through the outer membrane the effect of the lambda receptor is to decrease the Km of the transport system without influencing the Vmax of substrate flux. The second protein is a periplasmic protein that is induced by growth on glycerol and is essential for transport of sn-glycerol-3-phosphate in whole cells but not in membrane vesicles. This protein has solely been identified by the use of a two-dimensional polyacrylamide gel electrophoresis of periplasmic proteins in wild-type and mutants defective in sn-glycerol-3-phosphate transport.