Structural Analysis and Evidence for Dynamic Emergence of Bacillus anthracis S-Layer Networks
AUTOR(ES)
Couture-Tosi, Evelyne
FONTE
American Society for Microbiology
RESUMO
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 Å, b = 83 Å, and γ = 106°, while those of Sap were a = 184 Å, b = 81 Å, and γ = 84°. 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.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=135436Documentos Relacionados
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