mtsA contains an lipoprotein peptidase cleavage site signal sequence as defined by Linton & Higgins [25]. To confirm that MtsA is a lipoprotein, the crude cell lysate of S. iniae HD-1

was mixed with Triton X-114, and the detergent phase was analyzed by western blotting using rabbit anti-MtsA antibodies (Figure 3B). The results showed that MtsA protein was extracted by Triton X-114. Together, the results indicated that MtsA protein is a lipoprotein. Figure 3 Analysis of the lipoprotein sequence patterns of MtsA by ScanProsite and the western blotting. (A) The mtsABC lipoprotein was assessed by ScanProsite. The results showed that amino acid residues D1 to D24 (MFKKISLAFAMLLSIFCITACSSQ) hit G+LPPv2 pattern, AZ 628 supplier and amino acid residues D17 to D21 (CITAC) hit PS51257 pattern. The symbol “”<"" indicates that the pattern

is restricted to the N terminus, and X is any amino acid. (B) Western blotting analysis results of the lipoproteins extracted learn more with Triton X-114. Purification of recombinant MtsA To be able to further characterize MtsA, we first expressed recombinant MtsA consisting of amino acid residues D27 to D310 that lacked the putative signal sequence. Briefly, mtsA gene was cloned and the PCR product was isolated from the plasmid after a double digestion with restriction enzymes BamHI and XhoI, and ligated into the compatible site of pET-32a-c (+) Vector to yield recombinant protein Calpain MtsA. The expressed MtsA had a molecular mass of 49.5-kDa (Figure 4) with a tag from Trx·Tag to EcoR V of pET-32a-c (+), which has a molecular weight of 17.7-kDa. The expression level of MtsA peaked after induction with 1 mM IPTG at 37°C for 4 h. The MtsA protein was purified from E. coli BL21 (DE3) under native condition n the soluble form and immunized the

New Zealand white rabbits. The results showed that the rabbit anti-MtsA antibody titers increased from essentially zero to 1:50,000 after four rounds of immunization (Additional file 1, Table S4). The western blotting analysis was performed to show the specificity of immunized sera against purified MtsA (Figure 4, and Additional file 2, Figure S3-4). Figure 4 SDS-PAGE and western blotting analysis of expressed and purified MtsA. Lanes 1~4, SDS-PAGE showing the purification results of MtsA. The gels were stained with Coomassie brilliant blue. Lane 1, molecular mass marker; lane 2, E. coli with control pet-32a-c (+) vector; lane 3, E. coli lysate containing MtsA (approximately 49.5-kDa); lane 4, purified MtsA (approximately 49.5-kDa). Lanes 5~7, western blotting results of purified MtsA. Lane 5, E. coli with control pet-32a-c (+) vector; lane 6, E. coli lysate containing MtsA (approximately 49.5-kDa); lane 7, purified MtsA (approximately 49.5-kDa).