Venom Profiling of the Insular Species : Characterization of Proteome, Glycoproteome, and N-Terminome Using Terminal Amine Isotopic Labeling of Substrates.

, a species endemic to Alcatrazes Islands, is regarded as critically endangered due to its small area of occurrence and the declining quality of its habitat. We recently reported the identification of N-glycans attached to toxins of species, showing similar compositions in venoms of the complex (, , and ). Here, we characterized venom using electrophoretic, proteomic, and glycoproteomic approaches. Electrophoresis showed that venom differs from and ; however, N-glycan removal revealed similarities between them, indicating that the occupation of N-glycosylation sites contributes to interspecies variability in the complex. Metalloproteinase was the major toxin class identified in the venom proteome followed by serine proteinase and C-type lectin, and overall, the adult venom resembles that of juvenile specimens. The comparative glycoproteomic analysis of venom with and indicated that there may be differences in the utilization of N-glycosylation motifs among their different toxin classes. Furthermore, we prospected for the first time the N-terminome of a snake venom using the terminal amine isotopic labeling of substrates (TAILS) approach and report the presence of ∼30% of N-termini corresponding to truncated toxin forms and ∼37% N-terminal sequences blocked by pyroglutamic acid in venom. These findings underscore a low correlation between venom gland transcriptomes and proteomes and support the view that post-translational processes play a major role in shaping venom phenotypes.