title: Point mutations in transmembrane helices 2 and 3 of ExbB and TolQ affect their activities in Escherichia coli K-12.
abstract: Replacement of glutamate 176, the only charged amino acid in the third transmembrane helix of ExbB, with alanine (E176A) abolished ExbB activity in all determined ExbB-dependent functions of Escherichia coli. Combination of the mutations T148A in the second transmembrane helix and T181A in the third transmembrane helix, proposed to form part of a proton pathway through ExbB, also resulted in inactive ExbB. E176 and T148 are strictly conserved in ExbB and TolQ proteins, and T181 is almost strictly conserved in ExbB, TolQ, and MotA.
authors.affiliation: Mikrobiologie/Membranphysiologie, Universität Tübingen, D-72076 Tübingen, Germany. volkmar.braun@mikrobio.uni-tuebingen.de
authors.forename: Volkmar
authors.initials: V
authors.lastname: Braun
authors.forename: Christina
authors.initials: C
authors.lastname: Herrmann
mesh_terms: D001426:Bacterial Proteins / Q000502:physiology; D004926:Escherichia coli / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000502:physiology*; D005291:Ferrichrome / Q000378:metabolism; D017354:Point Mutation; D017433:Protein Structure, Secondary; D013329:Structure-Activity Relationship
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C052874:ExbB protein, E coli; C064779:MotB protein, Bacteria; C060792:tolQ protein, E coli; D005291:Ferrichrome