DNA HYDROLYSIS BY MONOCLONAL ANTI-SSDNA AUTOANTIBODY BV-04-01 - ORIGINS OF CATALYTIC ACTIVITY

Monoclonal anti-DNA autoantibody BV 04-01 catalyzed hydrolysis of DNA in the presence of Mg2+ ions. DNA hydrolyzing activity was associated with BV 04-01 IgG, Fab, and SCA 04-01 proteins. Pronounced cleavage sp ecificity for both ss and dsDNA was observed with efficient hydrolysis of the C-rich region of the oligonucleotide A(7)C(7)ATATAGCGCGT(7) as well as preference for cleavage within CG-rich regions of double-stra nded DNA. Data on specificity of ssDNA hydrolysis and kinetic data obt ained from wild-type SCA 04-01 and two SCA 04-01 mutants (L32Phe and L 27dHis) were used to model the catalytically active antibody site util izing the previously resolved X-ray structure of (dT)(3) liganded Fab 04-01. The resulting model suggested that BV 04-01 activates the targe t phosphodiester bond by induction of conformational strain. In additi on, the antibody-DNA complex contained a potential Mg2+ ion coordinati on site composed of the L32Tyr and L27dHis amino acid side chains and a DNA 3'-phosphodiester group. Induction of strain and metal coordinat ion could be constituents of a mechanism by which this antibody cataly zed DNA hydrolysis. Sequence data for BV 04-01 V-H and V-L genes sugge sted that the proposed catalytic antibody active site was germ-line en coded. This observation suggests the hypothesis that catalytic activit y might represent an important but unspecified function of some antibo dy molecules. (C) 1998 Elsevier Science Ltd. All rights reserved.