title: Mutational and sequence analysis of transmembrane segment 6 orientation in TetA proteins.
abstract: The packing orientations of the 8 transmembrane (TM) segments that line the central, aqueous transport channel within tetracycline resistance proteins (TetA) have been established. However, the orientations of the remaining 4 segments, TMs 3, 6, 9, and 12, located at the periphery, and away from the transport channel, have not yet been determined. In this study, the packing orientation of TM6 within the class C TetA protein encoded by plasmid pBR322 was evaluated by substitution mutagenesis and analysis of sequence conservation and amphipathicity. The combined data support a model in which the conserved and polar face of the TM6 alpha-helix containing Asn170 and Asn173 orients towards channel-lining TM segments, and the relatively non-conserved and hydrophobic face of TM6 points towards membrane lipids.
authors.affiliation: Department of Molecular Biology, University of Wyoming, P.O. Box 3944, Laramie, WY 82071-3944, USA.
authors.forename: G Shane
authors.initials: GS
authors.lastname: Lewis
authors.forename: Jean E
authors.initials: JE
authors.lastname: Jewell
authors.forename: Tzulip
authors.initials: T
authors.lastname: Phang
authors.forename: Kurt W
authors.initials: KW
authors.lastname: Miller
mesh_terms: D000595:Amino Acid Sequence; D017920:Antiporters / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004252:DNA Mutational Analysis; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D020539:Sequence Analysis, Protein
chemical_list: D017920:Antiporters; D001426:Bacterial Proteins; C079051:tetA protein, Bacteria