Erschienen:
International Union of Crystallography (IUCr), 2014
Erschienen in:Acta Crystallographica Section D Biological Crystallography
Sprache:
Nicht zu entscheiden
DOI:
10.1107/s1399004714007482
ISSN:
1399-0047
Entstehung:
Anmerkungen:
Beschreibung:
<jats:p>Outer membrane protein (OMP) biogenesis is an essential process for maintaining the bacterial cell envelope and involves the β-barrel assembly machinery (BAM) for OMP recognition, folding and assembly. In<jats:italic>Escherichia coli</jats:italic>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<jats:italic>E. coli</jats:italic>BamA β-barrel and P5 domain was determined at 3 Å resolution. These data add information beyond that provided in the recently published crystal structures of BamA from<jats:italic>Haemophilus ducreyi</jats:italic>and<jats:italic>Neisseria gonorrhoeae</jats:italic>and are a valuable basis for the interpretation of pertinent functional studies. In an `open' conformation,<jats:italic>E. coli</jats:italic>BamA displays a significant degree of flexibility between P5 and the barrel domain, which is indicative of a multi-state function in substrate transfer.<jats:italic>E. coli</jats:italic>BamA is characterized by a discontinuous β-barrel with impaired β1–β16 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.</jats:p>