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Immunochemical Characteristics and Rheumatoid Factor Inhibiting Activity of Enzymic Subfragments from the Cγ3 Homology Region of Human IgG
Author(s) -
OKAFOR G. O.,
TURNER M. W.
Publication year - 1974
Publication title -
scandinavian journal of immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.934
H-Index - 88
eISSN - 1365-3083
pISSN - 0300-9475
DOI - 10.1111/j.1365-3083.1974.tb01246.x
Subject(s) - elastase , homology (biology) , rheumatoid factor , microbiology and biotechnology , chemistry , antigen , biochemistry , pancreatic elastase , amino acid , asparagine , residue (chemistry) , antibody , biology , stereochemistry , enzyme , immunology
Subfragments of the pFc' fragment of human IgG (C γ 3 homology region), obtained by mild proteolysis with ficin, elastase, and subtilsin, have been chemically characterized and studied for their ability to interact with a rheumatoid factor with anti‐Gm(a) specificity. Amino acid composition and terminal amino acid data indicate that the subfragments difter in only one or two amino acid residues. Probable molecular locations for the subfragments, in terms of the sequenced γ 1‐chain, are proposed as follows: ficin fragment, residues 340–433; elastase fragment, 340–434; subtilsin fragment, 340–432. The subtilsin and ficin subfragments did not inhibit the passive haemagglutination of sheep erythrocytes coated with pFc' fragment by a rheumatoid serum with anti‐Gm(a) specificity. The elastase fragment was weakly inhibitory, and it is suggested that this may represent further evidence that the asparagine residue at position 434 is involved, as a noncorrelative determinant, in the expression of the Gm(a) antigen. The data also suggest that the antigen interacting with rheumatoid anti‐Gm(a) is structurally identical to the antigen interacting with anti‐Gm(a) from a sensitized donor.