Figure 3.

Sequence homology of the calcin family and molecular models of hadrucalcin (HdCa). (A) Sequence alignment of HdCa with other scorpion peptides that activate ryanodine receptors. Imperatoxin A (IpTx_a) from Pandinus imperator (Zamudio et al., 1997) maurocalcin (MCa) from Scorpio maurus (Faljoun et al., 2000), opicalcin 1 and 2 are sequences predicted from Opistophthalmus carinatus (Zhu et al., 2003). (B) Homology model of HdCa compared with MCa. The model was based on the atomic coordinates of MCa, with which it has the highest degree of sequence identity, using the programme Sybyl (Tripos, Inc.). (C) Orientation of basic residues (blue) on the globular structures of IpTx_a (left), HdCa (middle) and MCa (right).