title: Membrane topology of the L-rhamnose-H+ transport protein (RhaT) from enterobacteria.
abstract: The L-rhamnose-H+ symporter (RhaT) is a 344-amino acid integral membrane protein, found in many Enterobacteria, which couples the uptake of the sugar L-rhamnose with the inward movement of protons. Based on its hydropathy profile and the application of von Heijne's "positive inside" rule (von Heijne, G. (1992) J. Mol. Biol. 225, 487-494), a model of the L-rhamnose-H+ symport protein (RhaT) is proposed containing 10 transmembrane helices with the NH2 and COOH termini in the periplasm. This model was tested by the creation of random beta-lactamase (Bla) fusions. The data from 33 unique, randomly generated, RhaT-Bla fusions and from 5 site-specific fusions supported the proposed topology between transmembrane helices 2-10. However, the localization of the putative first hydrophilic loop and the NH2 terminus was not possible because the beta-lactamase fusions in this region were shown to be unreliable indicators of the topology of RhaT.
authors.affiliation: Department of Biochemistry, University of Cambridge, United Kingdom.
authors.forename: C G
authors.initials: CG
authors.lastname: Tate
authors.forename: P J
authors.initials: PJ
authors.lastname: Henderson
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics; D001483:Base Sequence; D015153:Blotting, Western; D004926:Escherichia coli / Q000737:chemistry; D029968:Escherichia coli Proteins; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000235:genetics; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics; D012210:Rhamnose; D012486:Salmonella typhimurium / Q000737:chemistry; D027981:Symporters; D001618:beta-Lactamases / Q000737:chemistry / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D011993:Recombinant Fusion Proteins; C067370:RhaT protein, E coli; D027981:Symporters; D001618:beta-Lactamases; D012210:Rhamnose