Clone And Expression Of S-layer Protein Gene Of Lactobacillus Helveticus

Lactobacilli are members of the lactic acid bacteria, a phylogenetically diverse group of Gram-positive bacteria characterized by the formation of lactic acid as a sole or main end product of their sugar fermentation. Lactobacilli are commonly found in nature and they are associated with a number of different habitats rich in carbohydrate or protein such as plants or spoiled food. Moreover, several Lactobacillus species are also members of the normal microbiota of human and animal gastrointestinal and genitourinary tracts, such as L.acidophilus, L brevis, L. helveticus.Surface layer proteins (S-layers, Slp) are crystalline arrays of proteinaceous subunits present as the outermost component of cell wall in several species of genus Lactobacillus, as well as in many other bacteria and Archaea. These proteins form a periodic ordered structure with oblique, square or hexagonal type symmetry. It is currently believed that these structures are formed due to entropy-driven self-assembly of the protein subunits, which are attached by non-covalent interactions.The functions of Slps are not yet completely revealed, but it has been proposed that these structures protect the microbe from hostile environmental agents and aid in maintaining cellular integrity and adhesion function. Several S-layer proteins have been reported to bind to epithelial cells, Caco-2 cells, mucus, DC (dendritic cell) and/or ECM components. In addition, S-layer protein extracts from L. helveticus have been reported to inhibit enterohaemorrhagic E. coli adhesion to host epithelial cells. In this study, the S-layer protein encoding gene was obtained by PCR, and expressed in E.coli JM109, and the main result as follow.1. Based on the S-layer protein gene of L. helveticus ATCC 15009, by virtue of primier5.0, the specific primer was designed, and the DNA was obtained by PCR.2. The S-layer protein gene of L. helveticus ATCC 15009 was expressed on the surface of E.coli JM109 successfully. Under the conditions of 20℃0.6 mM IPTG and aerobic culturing at 150rpm, the production of protein was large. And the protein was purified by Ni-NTA superflow.