DNA hydrolysis by monoclonal autoantibody BV 04-01

Monoclonal anti-DNA autoantibody BV 04-01 catalyzed hydrolysis of DNA in th e presence of Mg2+. Catalysis was associated with BV 04-01 IgG, Fab, and si ngle-chain-antibody (SCA) proteins. Cleavage of both ss and dsDNA was obser ved with efficient hydrolysis of the C-rich region of A(7)C(7)ATATAGCGCGT(2 ), as well as a preference for cleaving within CG-rich regions of dsDNA. Da ta on specificity of ssDNA hydrolysis and kinetic data obtained from wild-t ype SCA, and two SCA mutants were used to model the catalytically active an tibody site using the previously resolved X-ray structure of BV 04-01. The resulting model suggested that the target phosphodiester bond is activated by induction of conformational strain. In addition, the antibody-DNA comple x contained a Mg2+ coordination site composed of the L32Tyr and L27dHis sid e chains and a DNA 3'-phosphodiester group. Induction of strain along with the metal coordination could be part of the mechanism by which this antibod y catalyzes DNA hydrolysis. Sequence data for BV 04-01 V-H and V-L genes su ggested that the proposed catalytic-antibody active site was germline-encod ed. This observation suggests that catalytic activity might represent an im portant-rarely examined-function for some antibody molecules.