Open AccessStructural evidence for independent joining region gene in immunoglobulin heavy chains from anti-galactan myeloma proteins and its potential role in generating diversity in complementarity-determining regions
Author(s) -
DN Rao,
Stuart Rudikoff,
Henry C. Krutzsch,
Michael Potter
Publication year - 1979
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.76.6.2890
Subject(s) - biology , galactan , gene , immunoglobulin heavy chain , amino acid , heavy chain , genetics , complementarity determining region , myeloma protein , peptide sequence , antibody , cell wall
We have determined the variable region sequences of four heavy chains from β(1-6)D-galactan-binding myeloma proteins. Two of these proteins are identical to position 100 which is located in the third complementarity-determining region (CDR-3). The remaining two differ at a total of 8 positions over the first 100 amino acids, and all of the differences can be explained by single-base mutations at the DNA level. When an assessment is made of the protein segment following CDR-3, which has been termed “J segment” or “FR4,” a completely different pattern of variation is observed. The J segments from the four proteins can be divided into two sets. Members of each set share a series of linked amino acids not found in members of the alternative set. The two proteins identical to position 100 have J segments from the two different sets, suggesting that recombination has occurred betweenV andJ genes. An examination of the CDR-3 sequences from the four heavy chains reveals substitutions at positions 100 and 105. Gly is found at 100 in two of the proteins and His in the remaining two. In the two proteins with Gly-100, the following J sequence is limited to one of the two sets of J segments defined by linked amino acids. Similarly, the two heavy chains with His-100 have J segments from the second set. Thus, at the protein level an apparent association is seen between CDR-3 and J segment. If CDR-3 should be found linked to J segment at the DNA level, a new mechanism would be introduced for increasing antibody diversity by recombining variousCDR-3 plusJ genes with genes coding for the remainder of the variable region. Alternatively, if CDR-3 were coded for by theV gene, then the recombination ofV withJ may provide an opportunity to introduce mutations inCDR-3 . In this case the linkage of amino acids in CDR-3 and the J segments would suggest that recognition signals are used such that certainV genes only pair with a givenJ gene.