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Publication Abstract from PubMed

Outer membrane protein (OMP) biogenesis is an essential process for maintaining the bacterial cell envelope and involves the beta-barrel assembly machinery (BAM) for OMP recognition, folding and assembly. In Escherichia coli this function is orchestrated by five proteins: the integral outer membrane protein BamA of the Omp85 superfamily and four associated lipoproteins. To unravel the mechanism underlying OMP folding and insertion, the structure of the E. coli BamA beta-barrel and P5 domain was determined at 3 A resolution. These data add information beyond that provided in the recently published crystal structures of BamA from Haemophilus ducreyi and Neisseria gonorrhoeae and are a valuable basis for the interpretation of pertinent functional studies. In an `open' conformation, E. coli BamA displays a significant degree of flexibility between P5 and the barrel domain, which is indicative of a multi-state function in substrate transfer. E. coli BamA is characterized by a discontinuous beta-barrel with impaired beta1-beta16 strand interactions denoted by only two connecting hydrogen bonds and a disordered C-terminus. The 16-stranded barrel surrounds a large cavity which implies a function in OMP substrate binding and partial folding. These findings strongly support a mechanism of OMP biogenesis in which substrates are partially folded inside the barrel cavity and are subsequently released laterally into the lipid bilayer.

Structure of BamA, an essential factor in outer membrane protein biogenesis.,Albrecht R, Schutz M, Oberhettinger P, Faulstich M, Bermejo I, Rudel T, Diederichs K, Zeth K Acta Crystallogr D Biol Crystallogr. 2014 Jun;70(Pt 6):1779-89. doi:, 10.1107/S1399004714007482. Epub 2014 May 30. PMID:24914988^[6]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.