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. 2003 Mar;71(3):1462–1469. doi: 10.1128/IAI.71.3.1462-1469.2003

FIG. 2.

FIG. 2.

Western blot analysis of the action of streptococcal IgA1 proteases on mutant antibody P227T. Digests run under reducing conditions were probed with an anti-human IgA α chain-specific peroxidase conjugate that bound to epitopes in the Fab region. P227T was untreated (lane 1) or digested with IgA1 proteases of S. pneumoniae SK690 (lane 2) (and in the presence of 25 mM EDTA [lane 8]), S. sanguis SK4 (lane 3), S. oralis SK10 (lane 4), S. mitis SK564 (lane 5), and the type 2 IgA1 protease of N. meningitidis HF13 (lane 6). Wild-type recombinant IgA1 treated with the latter enzyme is shown in lane 7. Positions of molecular mass markers (in kilodaltons) are indicated on the left. Antibody P227T was resistant to cleavage by the IgA1 proteases of S. sanguis SK4 andS. mitis SK564 but was cleaved by the EDTA-sensitive IgA1 protease of S. pneumoniae and partially cleaved by the protease of S. oralis SK10 to give Fab fragments with masses consistent with cleavage at or near the peptide bond between residues 227 and 228 and different in mass from that resulting from cleavage with N. meningitidis type 2 IgA1 protease.