One-dimensional peptide mapping of the subunits of pertussis toxin

Pertussis toxin (pertussigen) purified from the cytoplasmic fraction of Bordetella pertussis strain 18334, phase 1, consisted of five subunits which included an additional subunit (S1a) not previously reported. Subunits S1, S1a and S2 showed extensive structural homology when analysed by one-dimensional peptide mapping, indicating that the latter two were probably derived from proteolytic cleavage of the largest subunit, S1. Subunits S3 and S4,5 generated only a limited number of peptides following chemical and enzymic degradation, but these subunits differed structurally from each other and from those showing structural homology.