Effect of somatic mutation on DNA binding properties of anti-DNA autoantibodies

Abstract

Autoantibodies that bind DNA are a hallmark of systemic lupus erythematosus. A subset of autoantibody•DNA complexes localize to kidney tissue and lead to damage and even death. 11F8, 9F11, and 15B10 are clonally related anti-DNA autoantibodies isolated from an autoimmune mouse. 11F8 binds ssDNA in a sequence-specific manner and causes tissue damage, while 9F11 and 15B10 bind ssDNA non-specifically and are benign. Among these antibodies, DNA binding properties are mediated by five amino acid differences in primary sequence. Thermodynamic and kinetic parameters associated with recognition of structurally different DNA sequences were determined for each antibody to provide insight toward recognition strategies, and to explore a link between binding properties and disease pathogenesis. A model of 11F8 bound to its high affinity consensus sequence provides a foundation for understanding the differences in thermodynamic and kinetic parameters between the three mAbs. Our data suggest that 11F8 utilizes the proposed ssDNA recognition motif including Y32 V L , a hydrogen bonding residue at 91 V L , and an aromatic residue at the tip of the third heavy chain complementarity determining region. Interestingly, a somatic mutation to arginine at 31 V H in 11F8 may afford additional binding site contacts including R31 V H , R96 V H , and R98 V H that could determine specificity. © 2007 Wiley Periodicals, Inc. Biopolymers 85: 471–480, 2007. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com