Abstract. Heavy chains of IgG, IgA, and IgM classes of human immunoglobulins were compared by N-terminal residue determination and partial amino acid sequence analysis. A third subclass of the variable region of heavy chains was observed; an unblocked glutamic acid as the N-terminal residue is characteristic of this subclass. Our results indicated that the heavy chain variable region subclasses are not class specific, and that a given heavy chain variable region may be found in association with constant regions for A-chains, a-chains, or y-chains of various subclasses.
Three immunogens with side chains of random amino acid sequence, poly (L Phe, l glu)-poly (DL Ala)--poly (L Lys) [(Phe, G)-A--L 223], poly (L Tyr, L Glu)-poly (DL Ala)--poly (L Lys) [(T, G)-A--L 509] and (T, G)-A-L 52, as well as two immunogens with side chains of defined amino acid sequences, GGT-A--L and TG-A--L, were sequenced using a Beckman automated sequenator. Despite the lack of a unique amino acid sequence for the amino terminus, reasonable results for the sequence studies were obtained using the Edman reaction. GGT-A--L and TG-A--L had 70% and 80% of their side chains respectively, with the desired sequence. The three compounds of random amino acid sequence were found to contain a large proportion of their A--L side chains unsubstituted. The side chains had a much greater probability of terminating in the aromatic amino acid than in the glutamic acid. The distribution of the length of side chains and their amino acid sequences was completely heterogeneous.
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