Sites of "spontaneous" degradation of IgD.

作者: Tony E. Hugli , Hans L. Spiegelberg , Sanna M. Goyert

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摘要: When 10 IgD myeloma proteins were examined by SDS-polyacrylamide gel electrophoresis (SDS-PAGE), the δ-chains of each protein showed multiple banding; average extrapolated m.w. for two major bands was 63,900 ± 735 and 60,550 675 daltons. compared to δ-chains, only e-chains not σ-, α- or µ-chains a banding pattern. Double reciprocal plots observed versus varying acrylamide concentrations demonstrated that all Ig heavy chains δ-chain mobility most variable. Digestion with yeast carboxypeptidase caused an initial release methionine proline, followed leucine, tyrosine, valine, serine. Carboxypeptidase A did any amino acids, whereas B released fractional molar quantities both lysine arginine. Therefore, native probably has Pro-Met-COOH carboxy-terminal sequence analogous Pro-Gly-COOH δ-chains. portion may have undergone degradation near COOH-terminus enzyme tryptic like specificity, thus explaining nominal basic residues CPB as well forms seen SDS-PAGE analysis. Tryptic Fc but Fab Fd fragments analysis which provides further evidence COOH-terminal region is responsible apparent heterogeneity. The NH 2 -terminal isolated from had “spontaneous” fragmentation during isolation analyzed. formed serum enzymes sequences in contrast generated trypsin gave singular sequence. Three cleavage sites deduced lysyl arginyl 6, 8 12 common half-cystine residue participates inter-heavy chain disulfide bond. These data demonstrate highly susceptible inter-Fd-Fc plasma trypsin-like specificity.

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