[1] Overview of bacterial ABC transporters

This chapter provides an overview of bacterial adenosine triphosphate-binding cassette (ABC) transporters, which contain a homologous adenosine triphosphate (ATP)-binding sequence. The short ATP-binding motifs also occur on transporters other than the ABC transporters, such as F-type ATPases, P-type ATPases, and the Ars arsenite/arsenate export system of E. coli. The ATP-binding domains or components of ABC transporters share homology in a larger region of about 200 amino acids, extending far beyond the Walker motifs or the ATP-binding cassettes in the narrow sense—the ABC family is defined on the basis of this and other evolutionary relationships. Several different types of ABC transporters are found in bacteria and they carry out a wide range of transport functions. Many transport small molecules into the cell in association with the binding protein (BP) that occurs in the periplasm of gram-negative bacteria or are anchored via a lipid moiety to the cytoplasmic membrane in gram-positive bacteria. The solutes transported by such systems include sugars, amino acids, peptides, phosphate esters, inorganic phosphate, sulfate, phosphonates, metal cations, iron–chelator complexes, vitamins, and polyamines.