Ultraviolet cross-linking of helical oligonucleotides to two monoclonal MRL-1pr/1pr anti-DNA autoantibodies. Variations in H and L chain binding to DNA.
 Experiments were performed to determine whether both H and L chains of different anti-native DNA autoantibodies are uniformly involved in binding to DNA.
 Two purified monoclonal mouse (MRL-1pr/1pr) IgG autoantibodies, H241 and 2C10, were tested.
 They both bound synthetic helical oligonucleotides of 10 to 20 base pairs in a gel electrophoresis retardation assay but differed in their preferences for given base sequences.
 Exposure of antibody-radiolabeled oligonucleotide mixtures to UV light (254 nm) for 10 min led to specific covalent cross-linking of oligonucleotide to both the H and the L chains of H241 but only to the H chain of 2C10.
 Single labeling events were detected without higher aggregation.
 The oligonucleotides were not cross-linked to unrelated IgG, even after 2 h of irradiation.
 Cross-linked (radioactively labeled) H and L chains of H241 and 2C10 were isolated from denaturing electrophoresis gels and digested with lysyl endopeptidase and/or staphylococcal V8 protease.
 H241 and 2C10 H chains each yielded a major labeled peptide fragment, but the peptides from the two antibodies were different.
 These experiments measured only some of the antibody-DNA interactions, probably with bases in the major groove of the DNA.
 They indicated that two MRL-1pr/1pr IgG anti-native DNA antibodies differ in their H and L chain contacts with DNA and provide an approach to identifying affinity-labeled binding sites in the antibodies.
