title: Characterization of a stalled complex on the β-barrel assembly machine.
abstract: The assembly of β-barrel proteins into membranes is mediated by an evolutionarily conserved machine. This process is poorly understood because no stable partially folded barrel substrates have been characterized. Here, we slowed the folding of the Escherichia coli β-barrel protein, LptD, with its lipoprotein plug, LptE. We identified a late-stage intermediate in which LptD is folded around LptE, and both components interact with the two essential β-barrel assembly machine (Bam) components, BamA and BamD. We propose a model in which BamA and BamD act in concert to catalyze folding, with the final step in the process involving closure of the ends of the barrel with release from the Bam components. Because BamD and LptE are both soluble proteins, the simplest model consistent with these findings is that barrel folding by the Bam complex begins in the periplasm at the membrane interface.
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138; Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138;
authors.forename: James
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138;
authors.forename: Mingyu
authors.initials: M
authors.lastname: Xue
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138;
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Wzorek
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138;
authors.forename: Tao
authors.initials: T
authors.lastname: Wu
authors.affiliation: Department of Molecular Biology, Princeton University, Princeton, NJ, 08544;
authors.forename: Marcin
authors.initials: M
authors.lastname: Grabowicz
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138;
authors.forename: Luisa S
authors.initials: LS
authors.lastname: Gronenberg
authors.affiliation: Department of Molecular Biology, Princeton University, Princeton, NJ, 08544;
authors.forename: Holly A
authors.initials: HA
authors.lastname: Sutterlin
authors.affiliation: Department of Microbiology, The Ohio State University, Columbus, OH 43210;
authors.forename: Rebecca M
authors.initials: RM
authors.lastname: Davis
authors.affiliation: Department of Microbiology, The Ohio State University, Columbus, OH 43210; ruiz.82@osu.edu tsilhavy@princeton.edu kahne@chemistry.harvard.edu.
authors.forename: Natividad
authors.initials: N
authors.lastname: Ruiz
authors.affiliation: Department of Molecular Biology, Princeton University, Princeton, NJ, 08544; ruiz.82@osu.edu tsilhavy@princeton.edu kahne@chemistry.harvard.edu.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Silhavy
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138; Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115 ruiz.82@osu.edu tsilhavy@princeton.edu kahne@chemistry.harvard.edu.
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Kahne
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding
chemical_list: D001425:Bacterial Outer Membrane Proteins; C503914:BamA protein, E coli; C513739:BamD protein, E coli; D029968:Escherichia coli Proteins; C475958:LptD protein, E coli; C514179:LptE protein, E coli
keywords: Bam complex; outer membrane; protein folding; β-barrel