The molecular basis for cross-reaction of an anti-dystrophin antibody with alpha-actinin.

The epitope recognised by the anti-dystrophin monoclonal antibodies MANDYS141 and MANDYS142 has been characterised using a phage display peptide library and a bacteriophage lambda cDNA library. Using a phage display library of random 15-mer peptides, the epitope recognised by the two antibodies was identified as EEXF. A lambda gt11 clone obtained by screening a human muscle cDNA library was shown to contain part of the out-of-frame human mitochondrial succinyl CoA synthetase (alpha-subunit) cDNA sequence which contains the sequence EEPL, suggesting a minimum requirement of EEXF/L for antibody binding. The sequence EEDF is located in the helical rod region of dystrophin and the N-terminal domain of alpha-actinin; this may explain why native dystrophin is not detected, since the alpha-helical, coiled-coil folding of the rod region of dystrophin may obscure the epitope in the native protein. The antibody cross-reaction between dystrophin and alpha-actinin is likely to be fortuitous and not due to any structural homology that exists between these two members of the spectrin superfamily.