All Gram-negative bacteria, mitochondria and chloroplasts have outer membrane proteins (OMPs) that perform many fundamental biological processes. The OMPs in Gram-negative bacteria are inserted and folded into the outer membrane by the β-barrel assembly machinery (BAM). The mechanism involved is poorly understood, owing to the absence of a structure of the entire BAM complex. Here we report two crystal structures of the Escherichia coli BAM complex in two distinct states: an inward-open state and a lateral-open state. Our structures reveal that the five polypeptide transport-associated domains of BamA form a ring architecture with four associated lipoproteins, BamB-BamE, in the periplasm. Our structural, functional studies and molecular dynamics simulations indicate that these subunits rotate with respect to the integral membrane β-barrel of BamA to induce movement of the β-strands of the barrel and promote insertion of the nascent OMP.
Journal article
2016-03-03T00:00:00+00:00
531
64 - 69
5
Bacterial Outer Membrane Proteins, Crystallography, X-Ray, Escherichia coli, Escherichia coli Proteins, Lipoproteins, Models, Molecular, Molecular Dynamics Simulation, Movement, Multiprotein Complexes, Periplasm, Protein Binding, Protein Structure, Tertiary, Protein Subunits, Rotation