A P-SUPERFAMILY TOXIN ENCODED FROM Conus regius cDNA

BRAGA, M.C.V.(1), FREITAS, J.C.(1), YAMANE, T.(2), RÁDIS-BAPTISTA, G.(2)

(1)IB, USP, (2)Instituto Butantan, São Paulo, SP, Brazil.

Each species of Conus has 50 to 200 different biologically active peptides, which are encoded in its venom duct. This variety of peptides is responsible for the efficient prey capture in this marine mollusk group. A new group of the conotoxins, the “P-superfamily”, is characterized by the presence of 6 cystein residues (-C-C-C-C-C-C-) and elicits a spasmodic activity in mice. In order to search for P-superfamily toxin precursors in the Brazilian mollusk Conus regius, collected in the Fernando de Noronha Archipelago, a cDNA library was constructed from poly(A⁺) RNA isolated from its venom duct. Based on the published sequence of conotoxins belonging to the P-Superfamily, a primer was designed, and a PCR homology screening initiated. The amplified cDNA was cloned and sequenced. The sequence analysis revealed a pre-propeptide with a highly conserved signal peptide sequence (96%). The non-cystein residues of the mature toxin show around 80% of divergence, while the cystein residues show 100% similarity, when compared against Tx9.1 and Gm9.1 from C. textile and C. gloriamaris, respectively. Based on signal peptide sequence similarity and the conserved position of cystein residues, it is highly probable that the present toxin belongs to the "P-superfamily" of conopeptides. In concordance with the nomenclature, it is designated Rg9.1.

Financial support: FAPESP

Acknowledgments: IBAMA, Águas Claras Diving Center, CEBIMar, USP and Instituto Butantan.

CORRESPONDENCE TO:

Maria Cristina Vianna Braga, Alameda dos Arapanés 309, Apto. 22, São Paulo, SP, CEP: 04524-000, Brasil, Email: mcbraga@usp.br