A novel high molecular weight metalloproteinase cleaves fragment F1 of activated human prothrombin

Peptidase specificity from the substrate cleavage collection in the MEROPS database and a tool to measure cleavage site conservation

One peptidase can usually be distinguished from another biochemically by its action on proteins, peptides and synthetic substrates. Since 1996, the MEROPS database (http://merops.sanger.ac.uk) has accumulated a collection of cleavages in substrates that now amounts to 66,615 cleavages. The total number of peptidases for which at least one cleavage is known is 1700 out of a total of 2457 different peptidases. This paper describes how the cleavages are obtained from the scientific literature, how they are annotated and how cleavages in peptides and proteins are cross-referenced to entries in the UniProt protein sequence database. The specificity profiles of 556 peptidases are shown for which ten or more substrate cleavages are known. However, it has been proposed that at least 40 cleavages in disparate proteins are required for specificity analysis to be meaningful, and only 163 peptidases (6.6%) fulfil this criterion. Also described are the various displays shown on the website to aid with the understanding of peptidase specificity, which are derived from the substrate cleavage collection. These displays include a logo, distribution matrix, and tables to summarize which amino acids or groups of amino acids are acceptable (or not acceptable) in each substrate binding pocket. For each protein substrate, there is a display to show how it is processed and degraded. Also described are tools on the website to help with the assessment of the physiological relevance of cleavages in a substrate. These tools rely on the hypothesis that a cleavage site that is conserved in orthologues is likely to be physiologically relevant, and alignments of substrate protein sequences are made utilizing the UniRef50 database, in which in each entry sequences are 50% or more identical. Conservation in this case means substitutions are permitted only if the amino acid is known to occupy the same substrate binding pocket from at least one other substrate cleaved by the same peptidase.

Albocollagenase, a novel recombinant P-III snake venom metalloproteinase from green pit viper (Cryptelytrops albolabris), digests collagen and inhibits platelet aggregation

Molecular cloning and functional characterization of P-III snake venom metalloproteinases (SVMPs) will give us deeper insights in the pathogenesis of viper bites. This may lead to novel therapy for venom-induced local tissue damages, the complication refractory to current antivenom. The aim of this study was to elucidate the in vitro activities of a new SVMP from the green pit viper (GPV) using recombinant DNA technology. We report, here, a new cDNA clone from GPV (Cryptelytrops albolabris) venom glands encoding 614 amino acid residues P-III SVMP, termed albocollagenase. The conceptually translated protein comprised a signal peptide and prodomain, followed by a metalloproteinase domain containing a zinc-binding motifs, HEXGHXXGXXH-CIM and 9 cysteine residues. The disintegrin-like and cysteine-rich domains possessed 24 cysteines and a DCD (Asp-Cys-Asp) motif. The albocollagenase deduced amino acid sequence alignments showed approximately 70% identity with other P-III SVMPs. Notably, the prodomain was highly conserved, while the metalloproteinase, disintegrin-like and cysteine-rich domains contained several differences. Albocollagenase without the signal peptide and prodomain was expressed in Pichia pastoris with an N-terminal six-histidine tag. After affinity purification from the supernatant of methanol-induced media, SDS-PAGE and Western blot analysis in both reducing and non-reducing conditions showed a protein band of approximately 62 kDa. The recombinant albocollagenase could digest human type IV collagen from human placenta basement membrane within 1 min. After 10-min incubation, it also inhibited collagen-induced platelet aggregation with 50% inhibitory concentration (IC₅₀) of 70 nM. This is the first report of the active recombinant SVMP enzymes expressed in P. pastoris. The results suggest the significant roles of P-III SVMP in local and systemic pathology of envenomated patients. Inhibitors of this SVMP will be investigated in further studies to find a better treatment for viper bites.

[Animal toxins and human disease: from single component to venomics, from biochemical characterization to disease mechanisms, from crude venom utilization to rational drug design]

Many animals produced a diversity of venoms and secretions to adapt the changes of environments through the long history of evolution. The components including a large quantity of specific and highly active peptides and proteins have become good research models for protein structure-function and also served as tools and novel clues for illustration of human disease mechanisms. At the same time, they are rich natural resources for new drug development. Through the valuable venomous animal resources of China, researchers at the Kunming Institute of Zoology, CAS have carried out animal toxin research over 30 years. This paper reviews the main work conducted on snake venoms, amphibian and insect secretions, and the development from single component to venomics, from biochemical characterization to human disease mechanisms, from crude venom to rational drug design along with a short perspective on future studies.

Purification and biochemical characterization of a novel hemorrhagic metalloproteinase from horned viper (Cerastes cerastes) venom

Snake venoms contain metalloproteinases that contribute to the local effects observed after envenoming. In this study, a hemorrhagic metalloproteinase (CcH1) was purified from Cerastes cerastes venom by a combination of gel filtration, ion exchange, affinity and RP-HPLC chromatography. The hemorrhagin was homogeneous on SDS-PAGE, with a molecular mass of 25 kDa. Isoelectric focusing revealed a pI of 5.5. CcH1 displayed hemorrhagic and proteolytic activities, but no esterolytic activity. The hemorrhagic and proteolytic activities of CcH1 were inhibited by EDTA and 1,10-phenanthroline, but not by PMSF, suggesting that this protein is a zinc-metalloproteinase. Furthermore, the hemorrhagic and proteolytic activities of CcH1 were stable in solution at up to 40 degrees C, with a loss of activity at > or =70 degrees C. The molecular mass and the inhibition assays suggest that the metalloproteinase CcH1 belongs to class P-I of SVMPs.

Effect of rACLF, a recombinant snake venom metallopeptidase on cell viability, chemokine expression and degradation of extracellular matrix proteins

Snake venom metallopeptidases (SVMPs) comprise a family of zinc-dependent enzymes, which display many different biological activities. ACLF is a 23kDa fibrinolytic non-hemorrhagic metallopeptidase from the venom of the snake Agkistrodon contortrix laticinctus. We have previously developed an expression system for production of recombinant ACLF (rACLF) in bacteria. To achieve a better understanding of the role of such enzyme in envenoming cases, we have studied the biological properties of rACLF, including the ability of enzyme to degrade extracellular proteins, as well its cytotoxic effect in human fibroblasts and HeLa cells. Our results showed that rACLF hydrolyzed laminin, fibronectin, type IV collagen and thrombospondin. rACLF decreased HeLa cell viability, changed cell morphology and induced detachment, while for human fibroblasts no cytotoxic effects were observed after treatment with rACLF. In addition, growth-related oncogene (GRO) and monocyte chemoattractant protein 1 (MCP-1/CCL2) were chemokines detected in the culture supernatant of human fibroblasts incubated with rACLF for 48h. These chemokines could contribute to the severe local lesion induced by Agkistrodon contortrix lacticinctus venom. These findings suggest a relevant role for ACLF in envenomation.

A snake venom metalloproteinase that inhibited cell proliferation and induced morphological changes of ECV304 cells

TSV-DM, a basic metalloproteinase with a molecular weight of 110kDa, was purified from Trimeresurus stejnegeri venom. TSV-DM degraded the Aalpha chain of fibrinogen more rapidly than the Bbeta chain in a dose dependent manner. The cDNA of TSV-DM encoded a polypeptide of 622 amino acid residues, which comprises a signal peptide, proprotein, metalloproteinase domain, spacer, disintegrin-like domain and cysteine-rich domain. The protein sequence deduced from cDNA was confirmed by peptide mass fingerprinting analysis. It is highly homologous to the members of subclass P-IIIb snake venom metalloproteinase, which comprises vascular apoptosis-inducing proteins. TSV-DM inhibited cell proliferation and induced cell morphologic changes transiently of ECV304 cells. However, DNA fragmentation and DNA content analysis demonstrated that this metalloproteinase could not induce ECV304 cells apoptosis.