Figure 3: Amino acid sequences and phylogenetic organization of Kunitz toxins. (A) Sequence alignment according to the MQ1 sequence. Greek letters indicate MQ1 secondary structures, α for alpha helix, β for beta strain. Arabic numbers design MQ1 loops, loop 1 from residue 7 to 20, loop 2 from residue 32 to 49, loop 3 from residue 25 to 29. Red: toxins from Mamba active on V2R. Green: toxins from cobra active on V2R. Blue: toxins from Mamba active on Kv1.1. Pink: toxins from Mamba active on Cav. Orange: BPTI. Black: Unknown activities. Underline names: peptides not active on V2R. Bold residues are different from MQ1. MQ1 red residues are specific for V2R Kunitz-type peptides. Calci: calcicludine P81658. BPTI: Bovine Pancreatic Trypsin Inhibitor. Id: percentage of sequence identity to MQ1. (B) Maximum likelihood (ML) tree of MQ proteins and related sequences obtained with RAxML. Branches with at least three sequences were annotated with the average frequency of ML tree bipartition among the 3000 trees with best posterior probabilities for each one of three chains of a MrBayes 3.2.6 run (top 1000 per run). Average bipartition frequency: 0.5-0.7, white circles; 0.7-0.9 grey circles; 0.9-1.0 black circles. Sequences in the alignment of panel A are highlighted in bold characters. Scale bar represents substitutions per site. Protein identifiers follow the same color scheme as panel A.