High-resolution architecture of the outer membrane of the Gram-negative bacteria Roseobacter denitrificans.
The outer membrane of Gram-negative bacteria protects the cell against bactericidal substances. Passage of nutrients and waste is assured by outer membrane porins, beta-barrel transmembrane channels. While atomic structures of several porins have been solved, so far little is known on the supramolecular structure of the outer membrane. Here we present the first high-resolution view of a bacterial outer membrane gently purified maintaining remnants of peptidoglycan on the perisplasmic surface. Atomic force microscope images of outer membrane fragments of the size of approximately 50% of the bacterial envelope revealed that outer membrane porins are by far more densely packed than previously assumed. Indeed the outer membrane is a molecular sieve rather than a membrane. Porins cover approximately 70% of the membrane surface and form locally regular lattices. The potential role of exposed aromatic residues in the formation of the supramolecular assembly is discussed. Finally, we present first structural data of the outer membrane porin from the marine Gram-negative bacteria Roseobacter denitrificans, and we perform a sequence alignment with porins of known structure.
Institut Curie, Equipe INSERM Avenir, UMR168-CNRS, 26 Rue d'Ulm, 75248 Paris Cedex 05, France.
Szymon
S
Jarosławski
Katia
K
Duquesne
James N
JN
Sturgis
Simon
S
Scheuring
D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry; D002462:Cell Membrane / Q000648:ultrastructure*; D018625:Microscopy, Atomic Force; D019897:Periplasm / Q000648:ultrastructure; D018272:Porins / Q000737:chemistry; D041904:Roseobacter / Q000737:chemistry / Q000648:ultrastructure*; D016415:Sequence Alignment
D001425:Bacterial Outer Membrane Proteins; D018272:Porins