title: Fold and function of polypeptide transport-associated domains responsible for delivering unfolded proteins to membranes.
abstract: Membranes of Gram-negative bacteria, mitochondria and chloroplasts receive and fold beta-barrel transmembrane proteins through the action of polypeptide transport-associated (POTRA) domains. In Escherichia coli, folding substrates are inserted into the outer membrane by the essential protein YaeT, a prototypic Omp85 protein. Here, the articulation between tandem POTRA domains in solution is defined by nuclear magnetic resonance (NMR) spectroscopy, indicating an unprecedented juxtaposition. The novel solution orientations of all five POTRA domains are revealed by small-angle X-ray scattering of the entire 46 kDa periplasmic region. NMR titration studies show that strands from YaeT's canonical folding substrate, PhoE, bind non-specifically along alternating sides of its mixed beta sheets, thus providing an ideal platform for helping to fold nascent outer-membrane proteins. Together, this provides the first structural model of how multiple POTRA domains recruit substrates from the periplasmic solution into the outer membrane.
authors.affiliation: Cancer Research UK Institute for Cancer Studies, School of Medicine, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Knowles
authors.forename: Mark
authors.initials: M
authors.lastname: Jeeves
authors.forename: Saeeda
authors.initials: S
authors.lastname: Bobat
authors.forename: Felician
authors.initials: F
authors.lastname: Dancea
authors.forename: Darren
authors.initials: D
authors.lastname: McClelland
authors.forename: Tracy
authors.initials: T
authors.lastname: Palmer
authors.forename: Michael
authors.initials: M
authors.lastname: Overduin
authors.forename: Ian R
authors.initials: IR
authors.lastname: Henderson
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000502:physiology*
chemical_list: D001425:Bacterial Outer Membrane Proteins; C503914:BamA protein, E coli; D029968:Escherichia coli Proteins