Figure 1.

Amino acid sequence determination of toxins. BgII: Direct sequencing by Edman degradation of reduced and alkylated toxin provided unequivocal identification of the 21 first amino acids, shown by underlining (-d->). Three additional fragments were obtained by HPLC separation of toxin BgII digested with Arg-C endopeptidase, which gave peptides with molecular masses of 1401.6, 1059.4 and 1259.4, respectively. The sequences were obtained by ionization, using MSIMS mass spectrometry, and correspond to sequence from positions 15 to 27, 28 to 36 and 37 to 48. The entire sequence corresponds exactly to that reported earlier (Loret et al., 1994). BgIII: Direct sequencing of reduced and alkylated toxin provided the 29 first amino acid residues, as indicated by the underlining (-d->). Three additional overlapping peptides were obtained by Arg-C endopeptidase digestion conducted as mentioned above for BgII, in which the only difference was found in the peptide corresponding to positions 15 to 27 (molecular mass 1402.6) where an aspartic acid substitutes an asparagine in position 16. The MSIMS spectrometry analysis confirmed the sequences shown, which also corresponds exactly to those earlier reported (Loret et al., 1994). The numbers on top of the sequences indicate the positions of the amino acids in the sequences.