title: Residues in the pathway through a membrane transporter.
abstract: The structure of solute transporters is understood largely from analysis of their amino acid sequences, and more direct information is greatly needed. Here we report work that applies cysteine scanning mutagenesis to describe structure-function relations in UhpT, a bacterial membrane transporter. By using an impermeant SH-reactive agent to probe single-cysteine variants, we show that UhpT transmembrane segment 7 spans the membrane as an alpha-helix and that the central portion of this helix is exposed to both membrane surfaces, forming part of the translocation pathway through this transporter.
authors.affiliation: Department of Physiology, Johns Hopkins Medical School, Baltimore, MD 21205, USA.
authors.forename: R T
authors.initials: RT
authors.lastname: Yan
authors.forename: P C
authors.initials: PC
authors.lastname: Maloney
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D001692:Biological Transport; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D003545:Cysteine; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins; D014644:Genetic Variation; D008961:Models, Structural; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D009004:Monosaccharide Transport Proteins; D011994:Recombinant Proteins; C063498:UhpT protein, E coli; D003545:Cysteine