Allosteric signalling in the outer membrane translocation domain of PapC usher

• DOI: 10.7554/elife.03532
• Publication Date: 2014-10-01T15:18:39Z
• Authors: Irene Farabella; Thieng Pham; Nadine S Henderson; Sebastian Geibel; Gilles Phan; David G Thanassi; Anne H Delcour; Gabriel Waksman; Maya Topf
• Keywords: Cell Membrane Permeability; QH301-705.5; Science; Amino Acid Motifs; Molecular Sequence Data; Gene Expression; Porins; Molecular Dynamics Simulation; bcs; outer membrane protein; Protein Structure, Secondary; Membrane Potentials; 03 medical and health sciences; Allosteric Regulation; evolution; structure; Biology (General); 0303 health sciences; Alanine; Escherichia coli Proteins; Q; R; dynamics; Biophysics and Structural Biology; Anti-Bacterial Agents; Erythromycin; Protein Structure, Tertiary; 3. Good health; Protein Subunits; Protein Transport; Amino Acid Substitution; Fimbriae, Bacterial; Mutation; Medicine; Signal Transduction

PapC ushers are outer-membrane proteins enabling assembly and secretion of P pili in uropathogenic E. coli. Their translocation domain is a large β-barrel occluded by a plug domain, which is displaced to allow the translocation of pilus subunits across the membrane. Previous studies suggested that this gating mechanism is controlled by a β-hairpin and an α-helix. To investigate the role of these elements in allosteric signal communication, we developed a method combining evolutionary and molecular dynamics studies of the native translocation domain and mutants lacking the β-hairpin and/or the α-helix. Analysis of a hybrid residue interaction network suggests distinct regions (residue ‘communities’) within the translocation domain (especially around β12–β14) linking these elements, thereby modulating PapC gating. Antibiotic sensitivity and electrophysiology experiments on a set of alanine-substitution mutants confirmed functional roles for four of these communities. This study illuminates the gating mechanism of PapC ushers and its importance in maintaining outer-membrane permeability.