His-Trap Affinity Chromatography Research Articles

Characterization of a recombinant β-glucosidase from the thermophilic bacterium Caldicellulosiruptor saccharolyticus

A recombinant beta-glucosidase from Caldicellulosiruptor saccharolyticus DSM 8903 with a specific activity of 13 U/mg was purified by heat treatment and His-Trap affinity chromatography and identified as a single 54 kDa band on SDS-PAGE. The molecular mass of the native enzyme was 108 kDa as a dimer by gel filtration. beta-Glucosidase showed optimum activity at pH 5.5 and 70 degrees C for p-nitrophenyl (pNP)-beta-d-glucopyranoside. The half-lives of the enzyme at 60, 70, and 80 degrees C were 250, 24.3, and 0.4 h, respectively. The enzyme exhibited catalytic efficiency and specific activity for pNP-beta-d-fucopyranoside, pNP-beta-d-glucopyranoside, and pNP-beta-d-galactopyranoside in decreasing order among aryl-beta-glycosides, but not for aryl-alpha-glycosides. Cello-oligosaccharides from n = 2 to 5 as substrates using 4 mM each sugar and 3 U/mg of enzyme were completely hydrolyzed to glucose at 70 degrees C within 16 h.

Characterization of a thermostable endo-1,5-α-l-arabinanase from Caldicellulorsiruptor saccharolyticus

A recombinant putative glycoside hydrolase from Caldicellulosiruptor saccharolyticus was purified with a specific activity of 12 U mg(-1) by heat treatment and His-Trap affinity chromatography, and identified as a single 56 kDa band upon SDS-PAGE. The native enzyme is a dimer with a molecular mass of 112 kDa as determined by gel filtration. The enzyme exhibited its highest activity when debranched arabinan (1,5-alpha-L-arabinan) was used as the substrate, demonstrating that the enzyme was an endo-1,5-alpha-L-arabinanase. The K (m), k (cat), and k (cat)/K (m) values were 18 mg ml(-1), 50 s(-1), and a 2.8 mg ml(-1) s(-1), respectively. Maximum enzyme activity was at pH 6.5 and 75 degrees C. The half-lives of the enzyme at 65, 70 and 75 degrees C were 2440, 254 and 93 h, respectively, indicating that it is the most thermostable of the known endo-1,5-alpha-L-arabinanases.

Cloning and Expression of Antibacterial Goat Lactoferricin from Escherichia coli AD494(DE3)pLysS Expression System

Goat lactoferricin (GLfcin), an antibacterial peptide, is released from the N terminus of goat lactoferrin by pepsin digestion. Two GLfcin-related cDNAs, GLfcin L and GLfcin S, encoding Ala20-Ser60 and Ser36-Ser60 of goat lactoferrin, respectively, were cloned into the pET-23a(+) expression vector upstream from (His)6-Tag gene and transformed into Escherichia coli AD494(DE3)pLysS expression host. After being induced by isopropyl-β-d -thiogalactopyranoside (IPTG), two (His)6-Tag fused recombinant lactoferricins, GLfcin L-His·Tag and GLfcin S-His·Tag, were expressed in soluble form within the E. coli cytoplasm. The GLfcin L-His·Tag and GLfcin S-His·Tag were purified using HisTrap affinity chromatography. According to an antibacterial activity assay using the agar diffusion method, GLfcin L-His·Tag had antibacterial activity against E. coli BCRC 11549, Staphylococcus aureus BCRC 25923, and Propionibacterium acnes BCRC 10723, while GLfcin S-His·Tag was able to inhibit the growth of E. coli BCRC 11549 and P. acnes BCRC 10723. These two recombinant lactoferricins behaved as thermostable peptides, which could retain their activity for up to 30 min of exposure at 100°C.

Secretion of proteases in serglycin transfected Madin–Darby canine kidney cells

Madin-Darby canine kidney (MDCK) cells, which do not normally express the proteoglycan (PG) serglycin, were stably transfected with cDNA for human serglycin fused to a polyhistidine tag (His-tag). Clones with different levels of serglycin mRNA expression were generated. One clone with lower and one with higher serglycin mRNA expression were selected for this study. 35S-labelled serglycin in cell fractions and conditioned media was isolated using HisTrap affinity chromatography. Serglycin could also be detected in conditioned media using western blotting. To investigate the possible importance of serglycin linked to protease secretion, enzyme activities using chromogenic substrates and zymography were measured in cell fractions and serum-free conditioned media of the different clones. Cells were cultured in both the absence and presence of phorbol 12-myristate 13-acetate (PMA). In general, enzyme secretion was strongly enhanced by treatment with PMA. Our analyses revealed that the clone with the highest serglycin mRNA expression, level of HisTrap isolated 35S-labelled serglycin, and amount of serglycin core protein as detected by western blotting, also showed the highest secretion of proteases. Transfection of serglycin into MDCK cells clearly leads to changes in secretion levels of secreted endogenous proteases, and could provide further insight into the biosynthesis and secretion of serglycin and potential partner molecules.