Amino acid sequence of the FV region of a human monoclonal IgM (NOV) with specificity for the capsular polysaccharide of the group B meningococcus and of Escherichia coli K1, which cross-reacts with polynucleotides and with denatured DNA

Abstract

The complete amino acid sequences of the VH and VL regions of a biologically significant Ig, IgMNOV, were determined. IgMNOV is reactive with the capsular polysaccharide of the group B meningococcus and of Escherichia coli K1. As reported earlier, it cross-reacts completely with polynucleotides poly(A) and poly(I) and to a lesser extent with denatured DNA and protects newborn rats against infection with E. coli K1, and is equal in potency to the standard horse anti-group B meningococcal serum. The reduced and alkylated chains were sequenced directly, identifying the L chain as lambda-subgroup II and the mu-H chain as subgroup III. The complete sequence of the VL region was determined by sequencing peptides generated by cleavage with Staphylococcus aureus protease, chymotrypsin, and trypsin. The H chain was cleaved with cyanogen bromide followed by enzymatic cleavages to obtain a large part of the VH region sequence. The structure was completed by sequencing tryptic peptides of the Fab fragment and by mass-spectrometric analysis.