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

短芽孢杆菌47具有形态学上独特的细胞壁结构，由两层蛋白质组成，称为外壁层和中壁层，以及肽聚糖层。中间壁层在细胞壁上形成晶格常数为14.5 nm的六边形阵列。对MW蛋白和OW蛋白的完整基因进行了克隆和测序，根据推导出的两种蛋白的氨基酸序列，几个特征变得明显。与OW蛋白相比，MW蛋白具有令人惊讶的亲水性。MW和OW蛋白的氨基酸组成与其他s层蛋白的化学氨基酸组成相似，均以酸性氨基酸为主，含硫氨基酸含量极低。利用从枯草芽孢杆菌中分离到的带有MW蛋白基因的MW蛋白，成功地重建了肽聚糖层的六边形排列结构。然而，当使用修饰的MW蛋白进行重构时，没有观察到晶体结构。最近，用倾斜视图电子显微镜重建了蛋白层的三维结构，分辨率为2nm。

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.