title: ABC transporters: one, two or four extracytoplasmic substrate-binding sites?
abstract: Two families of ATP-binding cassette (ABC) transporters in which one or two extracytoplasmic substrate-binding domains are fused to either the N- or C-terminus of the translocator protein have been detected. This suggests that two, or even four, substrate-binding sites may function in the ABC transporter complex. This domain organization in ABC transporters, widely represented among microorganisms, raises new possibilities for how the substrate-binding protein(s) (SBPs) might interact with the translocator. One appealing hypothesis is that multiple substrate-binding sites in proximity to the entry site of the translocation pore enhance the transport capacity. We also discuss the implications of multiple substrate-binding sites in close proximity to the translocator in terms of broadened substrate specificity and possible cooperative interactions between SBPs and the translocator.
authors.affiliation: Department of Biotehnology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, The Netherlands.
authors.forename: Tiemen
authors.initials: T
authors.lastname: van der Heide
authors.forename: Bert
authors.initials: B
authors.lastname: Poolman
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry; D001665:Binding Sites; D008969:Molecular Sequence Data; D010802:Phylogeny; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D011993:Recombinant Fusion Proteins