Cloning of the surface layer gene from Lactobacillus acidophilus ATCC 4356 and its heterologous expression and purification

Lactobacillus acidophilus ATCC 4356, like many other bacteria, harbours a surface layer consisting of aprotein (S-protein) of 44.2 kDa organized in regular arrays. The gene encoding this protein has been cloned in Escherichiacoli and sequenced. SlpA gene consists of 1360 nucleotides that has been amplified by PCR and the fragment has beencloned in E. Coli BL21. S-layer monomers expression has been verified by SDS-PAGE and the molecular mass was thesame as predicted size. Moreover, Purification of S-layer subunits on Ni-NTA column was conducted. Sequencecomparison of S-protein of with the other S-proteins from various species shows 78% similarity with Lactobacillushelveticus ATCC 12046. Additionally, the presence of two domains has been suggested, one comprising the N-terminaltwo-thirds (SAN) and another made up of the C-terminal one-third (SAC) of S-protein. The sequence of the N-terminaldomains is changeable, while that of the C-terminal domain is highly conserved in the S-proteins of these organisms. Thecapacity of S-protein of L. acidophilus as a probiotic makes it suitable for application as an oral delivery vehicle in thefields of nanobiotechnology.

Keywords:

Surface layer protein , Lactobacillus acidophilus ATCC 4356 , Cloning , Expression , TransmissionElectron Microscopy (TEM)