Recombinant expression and affinity purification of snake venom gland parvalbumin in Escherichia coli

Expression, purification and characterization of recombinant plasminogen activator from Gloydius brevicaudus venom in Escherichia coli

The plasminogen activator (PA) in snake venom, a serine protease, can convert plasminogen to active plasmin, indirectly causing the degradation of fibrin. It is difficult to purify sufficient snake venom PA (SV-PA) for clinical applications due to the low SV-PA content in venom. The gene encoding PA was obtained from the venom gland of Gloydius brevicaudus using RT-PCR with primers designed according to the N-terminal amino acids of G. brevicaudus venom PA (GBV-PA), was cloned into the prokaryotic expression vector pET-42a, and recombinant GBV-PA (rGBV-PA) was expressed via Isopropyl-β-d-1-Thiogalactopyranoside (IPTG) induction. Like human tissue PA, the purified renatured rGBV-PA could significantly reduce the rabbit plasma euglobulin lysis time (ELT) and prevent thrombus formation in the inferior vena cava of rats. Within the dosage range, the dosage and effects were positively correlated.

Fusion expression and purification of four disulfide-rich peptides reveals enterokinase secondary cleavage sites in animal toxins

Animal toxins are powerful tools for testing the pharmacological, physiological, and structural characteristics of ion channels, proteases, and other receptors. However, most animal toxins are disulfide-rich peptides that are difficult to produce functionally. Here, a glutathione S-transferase (GST) fusion expression strategy was used to produce four recombinant animal toxin peptides, ChTX, StKTx23, BmP01, and ImKTx1, with different isoelectric points from 4.7 to 9.2. GST tags were removed by enterokinase, a widely used and effective commercial protease that cleaves after lysine at the cleavage site DDDDK. Using this strategy, two disulfide-rich animal toxins ChTX and StKTx23 were obtained successfully with a yield of approximately 1-2 mg/l culture. Electrophysiological experiments further showed that these two recombinant toxins showed good bioactivities, indicating that our method was effective in producing large amounts of functional disulfide-rich animal toxins. Interestingly, by analyzing the separated fractions of BmP01, StKTx23, and ImKTx1 using matrix-assisted laser desorption ionization time-of-flight mass spectrometry, four new enterokinase secondary cleavage sites were found, consisting of the sequences "WEYR," "EDK," "QNAR," and "DNDK." To our knowledge, this is the first report of the presence of secondary cleavage sites for commercial enterokinase in animal toxins. These findings will help us use commercial enterokinase appropriately as a cleavage tool in the production of animal toxins.

Phylogenetic analysis of serine proteases from Russell's viper (Daboia russelli siamensis) and Agkistrodon piscivorus leucostoma venom

Serine proteases are widely found in snake venoms. They have variety of functions including contributions to hemostasis. In this study, five serine proteases were cloned and characterized from two different cDNA libraries: factor V activator (RVV-V), alpha fibrinogenase (RVAF) and beta fibrinogenase (RVBF) from Russell's viper (Daboia russelli siamensis), and plasminogen activator (APL-PA) and protein C activator (APL-C) from Agkistrodon piscivorus leucostoma. The snake venom serine proteases were clustered in phylogenetic tree according to their functions. K(A)/K(S) values suggested that accelerated evolution has occurred in the mature protein coding regions in cDNAs of snake venom serine proteases.

Application and expression of HSV gG1 protein from a recombinant strain

According to the homologous sequence of glycoprotein G1 (gG1) genes from different strains of herpes simplex virus type 1 (HSV-1), a pair of primers was designed to amplify the gG1 gene fragment by PCR. Both the PCR product and the pGEX-4T-1 vector were digested with EcoR I and Sal I. The gG1 gene fragment was subcloned into the digested pGEX-4T-1 vector to construct a recombinant plasmid (pGEX-4T-1-gG1). The resultant plasmid was identified by dual-enzyme digestion and sequence analysis, and then transformed into Escherichia coli BL21 for expression under the induction of isopropyl β-D-1-thiogalactoside (IPTG). The expressed GST-gG1 fragment was detected by SDS-PAGE and purified by affinity chromatography. The properties of GST-gG1 fragment were evaluated by immunoblot analysis. Enzyme-linked immunosorbent assays (ELISAs) based on the GST-gG1 fragment were used for determining IgG or IgM to HSV-1. The GST-gG1 fragment-specific ELISA was also compared with ELISA with whole-HSV-1 antigen and commercial ELISA kits. The gG1-specific IgG and IFN-γ producing CD8+ T cells were induced in mice immunized with the GST-gG1 fragment. These results indicated that the GST-gG1 fragment could be used for replacing whole-virus antigen to detect IgM and IgG to HSV-1 in human sera, which provided a strategy for developing vaccines to protect HSV-1 infection using gG1 fragment.