Molecular assembly mechanism on pseudocrystalline surface layer of B. brevis 47

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B. brevis 47 has a morphologically unique cell wall structure consisting of two protein layers, termed the outer and middly wall layers, and a peptidoglycan layer. The middle wall layer forms a hexagonal array with a lattice constant of 14.5 nm in the cell wall.Entire genes for the MW and OW proteins have been cloned and sequenced, based on the deduced amino acid sequences of both proteins, several features become evident. MW protein is surprisingly hydrophilic compared to OW protein. The amino acid compositions of MW and OW proteins are similar to the chemical amino acid compositions of other S-layer proteins in the predominance of acidic amino acids and in the very low content of sulfur-containing amino acids.We succeeded to reconstitute the hexagonally arranged structure on the peptidoglycan layer utilizing MW protein which was isolated from B. subtilis carrying the MW protein gene. No crystalline structures were, however, observed when modified MW proteins were used for the reconstitution.The three dimensional structure of MW protein layer has, recently, been reconstructed from tiltedview electron micrographs to a resolution of 2 nm.