9MGF

beta-barrel assembly machine from Escherichia coli in a middle state of substrate assembly

Summary for 9MGF

• Entry DOI: 10.2210/pdb9mgf/pdb
• EMDB information: 48254
• Descriptor: Outer membrane protein assembly factor BamA, Outer membrane protein assembly factor BamB, Outer membrane protein assembly factor BamC, ... (7 entities in total)
• Functional Keywords: beta-barrel assembly machine, outer membrane, folding intermediate, membrane protein
• Biological source: Escherichia coli K-12; More
• Total number of polymer chains: 7
• Total formula weight: 263758.77

Authors

Thomson, B.D.,Kahne, D. (deposition date: 2024-12-10, release date: 2025-12-17, Last modification date: 2026-04-15)

Primary citation

Thomson, B.D.,Marquez, M.D.,Rawson, S.,Dos Santos, T.M.A.,Harrison, S.C.,Kahne, D.
Structures of folding intermediates on BAM show diverse substrates fold by a conserved mechanism.
Proc.Natl.Acad.Sci.USA, 123:e2534936123-e2534936123, 2026

PubMed Abstract: The outer membranes of mitochondria, chloroplasts, and Gram-negative bacteria contain β-barrel membrane proteins that are assembled by conserved multisubunit machines. In bacteria, the β-barrel assembly machine (BAM) folds over a hundred compositionally different substrates into barrels that vary greatly in size. Some larger barrels require globular proteins to plug the barrel lumen. How a single machine can assemble such different barrels is unknown. Here we report three structures representing progressively folded stages of a 16-stranded barrel engaged with BAM, as well as the structure of a late-stage folding intermediate of a 26-stranded substrate folding around its soluble lipoprotein plug on BAM. We find that BAM catalyzes folding of these substrates by a uniform mechanism in which BAM undergoes major distortions to accommodate the nascent barrel.

PubMed: 41926538
DOI: 10.1073/pnas.2534936123

Experimental method

ELECTRON MICROSCOPY (3.3 Å)