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

Bothrops alcatraz, 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 Bothrops species, showing similar compositions
in venoms of the B. jararaca complex
(B. jararaca, B. insularis, and B. alcatraz). Here, we characterized B. alcatraz venom using electrophoretic, proteomic,
and glycoproteomic approaches. Electrophoresis showed that B. alcatraz venom differs from B.
jararaca and B. insularis; however, N-glycan removal revealed similarities between them, indicating
that the occupation of N-glycosylation sites contributes to interspecies
variability in the B. jararaca complex.
Metalloproteinase was the major toxin class identified in the B. alcatraz venom proteome followed by serine proteinase
and C-type lectin, and overall, the adult B. alcatraz venom resembles that of B. jararaca juvenile specimens. The comparative glycoproteomic analysis of B. alcatraz venom with B. jararaca and B. insularis 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 B. alcatraz 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.