title: Structural analysis and evidence for dynamic emergence of Bacillus anthracis S-layer networks.
abstract: Surface layers (S-layers), which form the outermost layers of many Bacteria and Archaea, consist of protein molecules arranged in two-dimensional crystalline arrays. Bacillus anthracis, a gram-positive, spore-forming bacterium, responsible for anthrax, synthesizes two abundant surface proteins: Sap and EA1. Regulatory studies showed that EA1 and Sap appear sequentially at the surface of the parental strain. Sap and EA1 can form arrays. The structural parameters of S-layers from mutant strains (EA1(-) and Sap(-)) were determined by computer image processing of electron micrographs of negatively stained regular S-layer fragments or deflated whole bacteria. Sap and EA1 projection maps were calculated on a p1 symmetry basis. The unit cell parameters of EA1 were a = 69 A, b = 83 A, and gamma = 106 degrees, while those of Sap were a = 184 A, b = 81 A, and gamma = 84 degrees. Freeze-etching experiments and the analysis of the peripheral regions of the cell suggested that the two S-layers have different settings. We characterized the settings of each network at different growth phases. Our data indicated that the scattered emergence of EA1 destabilizes the Sap S-layer.
authors.affiliation: Groupe de Microscopie Structurale Moléculaire (CNRS URA 2185), Institut Pasteur, Paris, France.
authors.forename: Evelyne
authors.initials: E
authors.lastname: Couture-Tosi
authors.forename: Hervé
authors.initials: H
authors.lastname: Delacroix
authors.forename: Tâm
authors.initials: T
authors.lastname: Mignot
authors.forename: Stéphane
authors.initials: S
authors.lastname: Mesnage
authors.forename: Mohamed
authors.initials: M
authors.lastname: Chami
authors.forename: Agnès
authors.initials: A
authors.lastname: Fouet
authors.forename: Gervaise
authors.initials: G
authors.lastname: Mosser
mesh_terms: D001408:Bacillus anthracis / Q000254:growth & development / Q000378:metabolism / Q000648:ultrastructure*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure*; D005613:Freeze Etching; D005614:Freeze Fracturing; D007091:Image Processing, Computer-Assisted; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D008854:Microscopy, Electron; D016624:Negative Staining
chemical_list: D001426:Bacterial Proteins; D008562:Membrane Glycoproteins; C055764:S-layer proteins