title: Crystal structure of β-barrel assembly machinery BamCD protein complex.
abstract: The β-barrel assembly machinery (BAM) complex of Escherichia coli is a multiprotein machine that catalyzes the essential process of assembling outer membrane proteins. The BAM complex consists of five proteins: one membrane protein, BamA, and four lipoproteins, BamB, BamC, BamD, and BamE. Here, we report the first crystal structure of a Bam lipoprotein complex: the essential lipoprotein BamD in complex with the N-terminal half of BamC (BamC(UN) (Asp(28)-Ala(217)), a 73-residue-long unstructured region followed by the N-terminal domain). The BamCD complex is stabilized predominantly by various hydrogen bonds and salt bridges formed between BamD and the N-terminal unstructured region of BamC. Sequence and molecular surface analyses revealed that many of the conserved residues in both proteins are found at the BamC-BamD interface. A series of truncation mutagenesis and analytical gel filtration chromatography experiments confirmed that the unstructured region of BamC is essential for stabilizing the BamCD complex structure. The unstructured N terminus of BamC interacts with the proposed substrate-binding pocket of BamD, suggesting that this region of BamC may play a regulatory role in outer membrane protein biogenesis.
authors.affiliation: Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada.
authors.forename: Kelly H
authors.initials: KH
authors.lastname: Kim
authors.forename: Suraaj
authors.initials: S
authors.lastname: Aulakh
authors.forename: Mark
authors.initials: M
authors.lastname: Paetzel
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018360:Crystallography, X-Ray; D048168:Escherichia coli K12 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D058635:Lipid-Linked Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D055550:Protein Stability; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary
chemical_list: D001425:Bacterial Outer Membrane Proteins; C556681:BamC protein, E coli; C513739:BamD protein, E coli; D029968:Escherichia coli Proteins; D058635:Lipid-Linked Proteins