ABSTRACT
The phospholipase A2 superfamily encompasses 15 groups that are classified into: secreted PLA2 (sPLA2); cytosolic PLA2 (cPLA2); Ca2+-independent intracellular PLA2 (iPLA2); platelet-activating factor acetylhydrolase (PAF-AH); and lysosomal PLA2. Currently, approximately 700 PLA2 sequences are known, of which 200 are obtained from the venom gland of Crotalinae snakes. However, thus far, little information is available on cloning, purification and structural characterization of PLA2 from Crotalus durisssus cascavela venom gland. In the present work, we report the molecular cloning of a novel svPLA2 from C. d. cascavella (Cdc), a predominant rattlesnake subspecies in northeastern Brazil. The Cdc svPLA2 cDNA precursor is 689 nucleotides long and encodes a protein of 138 amino acid residues, with a calculated molecular mass of approximately 13,847 Da and an estimated isoelectric point of 5.14. Phylogenetic analysis of Crotalinae PLA2 reveals that Cdc PLA2 clustered with other acidic type IIA PLA2 homologues is also present in the venom of North American rattlesnakes. Hitherto, this study presents a novel PLA2 cDNA precursor from C. d. cascavella and data reported herein will be useful for further steps in svPLA2 purification and analysis.
Subject(s)
Animals , Male , Cloning, Molecular , Crotalid VenomsABSTRACT
The first low-molecular-mass metalloprotease presenting prothrombin activating activity was purified from Bothrops insularis venom and named insularinase A. It is a single-chain protease with a molecular mass of 22 639 Da. cDNA sequence analysis revealed that the disintegrin domain of the precursor protein is post-translationally processed, producing the mature insularinase A. Analysis of its deduced amino acid sequence showed a high similarity with several fibrin(ogen)olytic metalloproteases and only a moderate similarity with prothrombin activators. However, SDS-PAGE of prothrombin after activation by insularinase A showed fragment patterns similar to those generated by group A prothrombin activators, which convert prothrombin into meizothrombin independently of the prothrombinase complex. In addition, insularinase A activates factor X and hydrolyses fibrinogen and fibrin. Chelating agents fully inhibit all insularinase A activities. Insularinase A induced neither detachment nor apoptosis of human endothelial cells and was also not able to trigger an endothelial proinflammatory cell response. Nitric oxide and prostacyclin levels released by endothelial cells were significantly increased after treatment with insularinase A. Our results show that, although its primary structure is related to class P-I fibrin(ogen)olytic metalloproteases, insularinase A is functionally similar to group A prothrombin activators.
