Clonagem e análise molecular de cDNAs do aparato peçonhento do peixe-escorpião Scorpaena plumieri (Bloch, 1789)

Abstract

Scorpionfish, members of the genera Scorpaena are known to be venomous, having venom glands tissues in ray-finned structures. Envenomation occurs through mechanical pressure on the spine, permiting the venom to escape producing a local and systemic damage in the prey. The present work describes the characterization of cDNAs obtained from Scorpaena plumieri venom apparatus. A total of 573 ESTs suitable for analysis were obtained from the bacteriophage library and categorized into different groups according to their biological functions. BLASTn analysis identified 39 (7%) for sequences involved in protein expression, 80 (14%) to metabolism, 46 (8%) to cell structure/motility, 103 (18%) to cell signaling/communication, 62 (11%) to regulatory genes, 81 (14%) to hypothetical proteins and 162 (28%) with unknown functions. The highly redundant message encoding for lectins-like proteins accounts for 69 (12%) of all transcripts obtained from Scorpaena plumieri. Based on the data obtained in RT-PCR and cDNA cloning, the nucleotide sequences encoding the α- and β-subunits toxin were successfully determined. The deduced amino acid sequence (702 amino acid residues each subunit) shows significant homology with toxins described in Scorpaeniformes. Sequence alignment between subunits displays an overall identity of 54% and a similarity of 76%. As reported for the Scorpaeniformes toxins, the subunits α and β toxin of the scorpionfish also contain a B30.2/SPRY domain in the C-terminal region. Potential sites for cytolytic and antimicrobial peptides were identified in both subunits. The phylogenetic tree generated for Scorpaeniformes toxins supports the classification of these fishes. These data indicate the presence of a putative toxin protein whose primary structure is alike other fish toxins and with potential for production of antivenom against scorpionfish envenomation in Brazil.