Molecular cloning of capillary permeability-increasing enzyme-2 from Agkistrodon caliginosus (Korean viper)

Cloning of serine protease cDNAs from Crotalus durissus terrificus venom gland and expression of a functional Gyroxin homologue in COS-7 cells

Gyroxin is one of main serine proteases of Crotalus durissus terrificus venom, representing about 2% of the protein content in the crude venom. It is a 33 kDa glycoprotein with 3.8% by weight of sugar moiety. This toxin induces hemotoxicity in mice and a neurological condition called barrel rotation syndrome. In the present work, we report the molecular cloning of five new nucleotide sequences from a cDNA library of the venom glands of a single specimen of C. d. terrificus. These sequences have been analyzed in silico with respect to their cDNA organization and similarity with other snake venom serine proteases (SVSPs). We also describe a rapid and efficient method for screening vectors for mammalian cell expression, based on the fact that SVSPs are difficult-to-express toxins due to the presence of several disulfide bonds and glycosylation in their structures. Thus, one of the Gyroxin cDNAs was subcloned into pSectag2 HygroA and pED vectors and used to transfect COS-7 cells. Expression of the functional recombinant Gyroxin isoform was achieved with this cell line with esterase activity in the conditioned culture medium, as revealed by immunoblot of secreted protein and standard anti-crotalic serum from Butantan Institute.

Identification and characterization of Harobin, a novel fibrino(geno)lytic serine protease from a sea snake (Lapemis hardwickii)

A gene encoding a novel serine protease designated as Harobin is cloned and identified from a sea snake venom gland bacteriophage T7 library. It has 265 amino acids and shares 50-70% similarity to terrestrial snake serine proteases. In addition to the 12 conservative Cys, it has three more Cys residues that may contribute to its higher enzymatic stability. Harobin is expressed in Pichia pastoris and purified. Recombinant Harobin exhibits an amidolytic activity, and specifically degrades Aalpha, Bbeta-chain of fibrinogen. It functions as a defibrase both in vitro and in vivo, and reduces thrombosis. Harobin prolongs the coagulation time and the bleeding time of mice and reduces the fibrinogen levels of rats as well. Meanwhile, intravenous injection of Harobin leads to the reduction of blood pressure in SHR rats. It results from the ability of Harobin that cleaves angiotensin I and release bradykinin from plasma kininogen in vitro and in vivo. These data suggest that Harobin is a novel defibrase and has a potential to be an agent for the therapy of thrombosis and hypertension.

Snake venom serine proteinases: sequence homology vs. substrate specificity, a paradox to be solved

Snake venom glands synthesize a variety of serine proteinases capable of affecting the haemostatic system. They act on macromolecular substrates of the coagulation, fibrinolytic, and kallikrein-kinin systems, and on platelets to cause an imbalance of the haemostatic system of the prey. In this review we describe their biochemical/biophysical characteristics, biological activities as well as aspects of their evolution and structure-activity relationship.

Serine protease isoforms of Deinagkistrodon acutus venom: cloning, sequencing and phylogenetic analysis

The major coagulating fibrinogenase of Deinagkistrdon acutus venom, designated acutobin, was purified by anion-exchange chromatography, gel filtration and reverse-phase HPLC. Approximately 80% of its protein sequence was determined by sequencing the various fragments derived from CNBr cleavage and digestion with endoprotease. Extensive screening of the venom gland cDNA species after amplification by PCR resulted in the isolation of four distinct cDNA clones encoding acutobin and three other serine proteases, designated Dav-PA, Dav-KN and Dav-X. The complete amino acid sequences of these enzymes were deduced from the cDNA sequences. The amino-acid sequence of acutobin contains a single chain of 236 residues including four potential N-glycosylation sites. The purified acutobin (40 kDa) contains approx. 30% carbohydrate by weight, which could be partly removed by N-glycanase. The phylogenetic tree of the complete amino acid sequences of 40 serine proteases from 18 species of Crotalinae shows functional clusters reflecting parallel evolution of the three major venom enzyme subtypes: coagulating enzymes, kininogenases and plasminogen activators. The possible structural elements responsible for the functional specificity of each subtype are discussed.

Sequence diversity of Vipera lebetina snake venom gland serine proteinase homologs--result of alternative-splicing or genome alteration

Four clones encoding homologous protein(ase)s were isolated from the Vipera lebetina (snake) venom gland cDNA library. One of them represented DNA encoding factor V activating enzyme (Siigur et al., 1999), the other is homologous to VLFVA but has two principal discrepancies in the translated protein sequence in comparison with snake venom serine proteinase structures: in the active site triad Ser195 is replaced by Asn195 and His57 by Arg57. The third and the fourth clone represent combinations of the first two clones. The possibilities of generation of such clones via trans-splicing of the primary gene transcript, by exon shuffling or by unequal crossing-over on the genome level are discussed.

cDNA cloning of brevinase, a heterogeneous two-chain fibrinolytic enzyme from Agkistrodon blomhoffii brevicaudus snake venom, by serial hybridization-polymerase chain reaction

Brevinase is a heterogeneous two-chain fibrinolytic enzyme, different from all of the known single-chain enzymes. A cDNA encoding brevinase was cloned from the venom gland of Agkistrodon blomhoffii brevicaudus by serial hybridization-PCR. Serial hybridization-PCR effectively amplified the complete cDNA of brevinase from the mixture of closely related transcripts. The cDNA sequence of 744 nucleotides was determined. The cDNA sequence included an open reading frame of 233 amino acids composed of an A chain (77 residues) and a B chain (156 residues). The deduced amino acid sequence included a potential N-glycosylation site (N54-X-S56), O-glycosylation site (Ser179), and RGD sequence. Brevinase included a unique Arg77 residue at the C-terminus of the A chain, distinguishing it from all of the compared homologous single-chain proteases. It could be assumed that a posttranslational cleavage site is located between Arg77 and Asn78. Based on the sequence similarity to those of the venom proteases, we could deduce that the critical catalytic residues are His40, Asn78, Asp85, and Ser179 and that the six potential disulfide bonds are Cys7-Cys138, Cys26-Cys41, Cys73-Cys231, Cys117-Cys185, Cys149-Cys164, and Cys175-Cys200. Despite the conservation of critical sequences, the phylogenetic tree showed that two-chain brevinase might be evolved separately from the homologous single-chain proteases.

Molecular cloning and sequence analysis of a cDNA for factor V activating enzyme

The complete amino acid sequence of a factor V activator (VLFVA) is deduced from the nucleotide sequence of a cDNA encoding the enzyme. The cDNA was isolated by PCR screening a venomous gland cDNA library of Central Asian Vipera lebetina snake. The full-length cDNA clone, derived from two overlapping fragments, comprises 1563 basepairs which encode an open reading frame of 259 amino acids. The amino acid sequence of VLFVA (235 amino acids) shows significant homology with snake venom and mammalian serine proteinases. It contains 12 half-cysteines which form, by analogy with other serine proteinases, 6 disulfide bridges. VLFVA has the catalytic triad His43-Asp88-Ser182. The amino terminal amino acid valine is preceded by 24 amino acids: a putative signal peptide of 18, mainly hydrophobic, amino acids and an activating peptide of 6, mainly hydrophilic amino acid residues. This is the first cloned factor V activating enzyme from snake venom.