Finally, plasmid DNA of positive clones was extracted and sequenced on ABI 377 DNA sequencer. Analysis of β-galactosidase

gene The open reading frame search from DNA sequences was carried out using ORF-finder (NCBI) (http://​www.​ncbi.​nlm.​nih.​gov/​), and database homology search was performed with BLAST program provided by NCBI. Furthermore, the multiple amino acid sequence alignment of Gal308 and known homologous β-galactosidases and the analysis of conserved selleck compound amino acid residues and active site residues of Gal308 were performed by using ClustalW2 program (http://​www.​ebi.​ac.​uk/​Tools/​msa/​clustalw2/​). Expression and purification of recombinant protein The PCR primers for gal308 amplification were listed as follows: gal308-f, 5′-CGCGGATCCATGGCCTTTCCAAACGAGCATGGAG, in which the BamHI site was shown in italics; gal308-r, 5′-CCCAAGCTTTCCCTCGTGTTCTTCATAGAC, in which the HindIII site was shown in italics. PCR reaction

conditions were: 98°C, 10 sec (denaturation); 68°C, 3 min (annealing and extension); repeated for 30 cycles. The PCR product was digested with BamHI/HindIII and subcloned to BamHI/HindIII-treated expression vector pET-32a (+) with a six-histidine tag for purification. The recombinant vector was transformed into E. coli BL21 (DE3), and then the cells were JNK inhibitor plated on LB agar containing 100 μg/ml ampicillin. The transformant was grown in a 100-ml flask containing 10 ml LB medium supplemented with 100 μg/ml ampicillin at 37°C until the optical density at 600 nm reached to 1.0, and then IPTG was added to final concentration of 1.2 mM, and the culture was incubated at 30°C for 8 h with shaking at 200 rpm. Cells were then collected

by centrifugation (6,000 g Y-27632 molecular weight for 20 min at 4°C) and stored at -20°C for later purification. All purification steps were performed according to the instruction of His Bind Purification Kit (Novagen). In brief, the cells were suspended in binding buffer (0.5 M NaCl, 5 mM imidazole, 20 mM Tris–HCl, pH 7.9) followed by sonication on ice. The supernatant was collected by centrifugation at 14,000 g for 20 min at 4°C, and then they were loaded onto a Ni-NTA His · Bind column (Novagen) pre-equilibrated with binding buffer. The column was washed with binding buffer and washing buffer (0.5 M NaCl, 60 mM imidazole, 20 mM Tris–HCl, pH 7.9). Finally, the bound protein was eluted with eluting buffer (1 M imidazole, 0.5 M NaCl, 20 mM Tris–HCl, pH 7.9). Next, the purified enzyme in elution buffer was collected and further removed imidazole by dialysis before the characterization of the enzyme. The dialysis was performed three times, and each dialysis lasted for two hours in dialysis buffer (100 mM NaCl, 3 mM dithiothreitol, 20 mM Tris–HCl, pH 7.9). Determination of molecular mass The molecular mass of the denatured protein was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Proteins were stained with Coomassie brilliant blue G-250.