Molecular and structural features of the proton-coupled oligopeptide transporter superfamily

Work in the area of molecular biology of transport proteins has unveiled the presence of a distinct peptide transporter superfamily whose members extend from the prokaryotic to the eukaryotic kingdom. There are two subgroups within this superfamily, one subgroup harnessing the energy necessary for active transport from a transmembrane H+ gradient and the other subgroup relying directly on ATP hydrolysis. In addition to the use of different driving forces, the two subgroups are also distinguishable with regard to molecular structure and operational mechanism. This review is intended to analyze critically the molecular nature of the members of the H+ gradient-dependent peptide transporter subgroup, with emphasis on the cloning strategies utilized in the isolation of the individual transporter cDNAs or genes; on the structural patterns, motifs, and conserved amino acid residues common to constituent members of the subgroup; and on the characteristic topological features of the individual members.