title: Projection structure and molecular architecture of OxlT, a bacterial membrane transporter.
abstract: The major facilitator superfamily (MFS) represents the largest collection of evolutionarily related members within the class of membrane 'carrier' proteins. OxlT, a representative example of the MFS, is an oxalate-transporting membrane protein in Oxalobacter formigenes. From an electron crystallographic analysis of two-dimensional crystals of OxlT, we have determined the projection structure of this membrane transporter. The projection map at 6 A resolution indicates the presence of 12 transmembrane helices in each monomer of OxlT, with one set of six helices related to the other set by an approximate internal two-fold axis. The projection map reveals the existence of a central cavity, which we propose to be part of the pathway of oxalate transport. By combining information from the projection map with related biochemical data, we present probable models for the architectural arrangement of transmembrane helices in this protein superfamily.
authors.affiliation: Laboratories of Biochemistry and Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Heymann
authors.forename: R
authors.initials: R
authors.lastname: Sarker
authors.forename: T
authors.initials: T
authors.lastname: Hirai
authors.forename: D
authors.initials: D
authors.lastname: Shi
authors.forename: J L
authors.initials: JL
authors.lastname: Milne
authors.forename: P C
authors.initials: PC
authors.lastname: Maloney
authors.forename: S
authors.initials: S
authors.lastname: Subramaniam
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D020624:Oxalobacter formigenes / Q000737:chemistry; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C099549:OxlT protein, bacteria; D011993:Recombinant Fusion Proteins