Snake venomics. Strategy and applications.

Snake bites can be deadly, but the venoms also contain components of medical and biotechnological value. The proteomic characterization of snake venom proteomes, snake venomics, has thus a number of potential benefits for basic research, clinical diagnosis, and development of new research tools and drugs of potential clinical use. Snake venomics is also relevant for a deep understanding of the evolution and the biological effects of the venoms, and to generate immunization protocols to elicit toxin-specific antibodies with greater specificity and effectiveness than conventional systems. Our snake venomics approach starts with the fractionation of the crude venom by reverse-phase HPLC, followed by the initial characterization of each protein fraction by combination of N-terminal sequencing, SDS-PAGE, and mass spectrometric determination of the molecular masses and the cysteine (SH and S--S) content. Protein fractions showing a single electrophoretic band, molecular mass, and N-terminal sequence can be straightforwardly assigned by BLAST analysis to a known protein family. On the other hand, protein fractions showing heterogeneous or blocked N-termini are analyzed by SDS-PAGE and the bands of interest subjected to automated reduction, carbamidomethylation, and in-gel tryptic digestion. The resulting tryptic peptides are then analyzed by MALDI-TOF mass fingerprinting followed by amino acid sequence determination of selected doubly and triply charged peptide ions by collision-induced dissociation tandem mass spectrometry. The combined strategy allows us to assign unambiguously all the isolated venom toxins representing over 0.05% of the total venom proteins to known protein families. Protocols and applications of snake venomics are reviewed and discussed.