Mutation of the surface chemistry is one of the prominent
characteristics of venom evolution. Estimation of the
accessible surface area ratio or the surface accessibility of
amino acid side chains revealed that 85 %of the episodically
adaptive sites in serine proteases were exposed, whilst only
15 % were buried (excluding the 6 sites that could not be
assigned to buried or exposed class), suggesting that most
mutations are focussed on the molecular surface (Fig. 7 and
Supplementary Table 5). The mutation of the surface
chemistry would not only increase the range of receptors
these toxins can target but could also help in evading the host
immune response. The remaining proportion of sites could
not be significantly assigned to either buried or exposed class
(Fig. 7 and Supplementary Table 5).