Abstract: Sortase (Srt) plays an important role in the adhesion of Gram-positive bacteria to host cells. The focus of this study was to recombine the sortase A (SrtA) of Lactobacillus acidophilus (Lap-SrtA) in E. coli and to evaluate the differences between Lap-SrtA with other pathogenic sortase. The srtA gene was cloned from L. acidophilus ATCC4356 and expressed in E. coli Transetta (DE3). The recombinant protein was purified and analyzed using Dabcyl-QALPTTGEE (Edans) as substrate. The results showed that the molecular weight of the recombinant protein was about 20 kDa with an Lap-SrtA activity, and the activity could be enhanced by Mg2+, Zn2+, and Mn2+. However, Ca2+ had no visible effect on the activity of SrtA, making it distinct from other pathogenic sortase. Chalcone could significantly inhibit SrtA activity. Furthermore, there were eight segments of β sheet structure in Lap-SrtA as analyzed by homology modeling using SWISS MODEL, and the active site residues of Lap-SrtA were found to be His 137, Cys 198 and Arg 205.

Key words: Lactobacillus acidophilus, sortase A, cloning, enzyme activity, structural characterization