title: Features of MotA proton channel structure revealed by tryptophan-scanning mutagenesis.
abstract: The MotA protein of Escherichia coli is a component of the flagellar motors that functions in transmembrane proton conduction. Here, we report several features of MotA structure revealed by use of a mutagenesis-based approach. Single tryptophan residues were introduced at many positions within the four hydrophobic segments of MotA, and the effects on function were measured. Function was disrupted according to a periodic pattern that implies that the membrane-spanning segments are alpha-helices and that identifies the lipid-facing parts of each helix. The results support a hypothesis for MotA structure and mechanism in which water molecules form most of the proton-conducting pathway. The success of this approach in studying MotA suggests that it could be useful in structure-function studies of other integral membrane proteins.
authors.affiliation: Department of Biology, University of Utah, Salt Lake City 84112, USA.
authors.forename: L L
authors.initials: LL
authors.lastname: Sharp
authors.forename: J
authors.initials: J
authors.lastname: Zhou
authors.forename: D F
authors.initials: DF
authors.lastname: Blair
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000737:chemistry*; D002462:Cell Membrane / Q000378:metabolism; D002465:Cell Movement; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000378:metabolism* / Q000502:physiology; D005407:Flagella / Q000502:physiology; D046911:Macromolecular Substances; D008961:Models, Structural; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010957:Plasmids; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D015183:Restriction Mapping; D017386:Sequence Homology, Amino Acid; D014364:Tryptophan
chemical_list: D001426:Bacterial Proteins; D046911:Macromolecular Substances; C063010:MotA protein, Bacteria; D011994:Recombinant Proteins; D014364:Tryptophan