THE MOLECULAR-BASIS FOR CROSS-REACTION OF AN ANTI-DYSTROPHIN ANTIBODYWITH ALPHA-ACTININ

The epitope recognised by the anti-dystrophin monoclonal antibodies MA NDYS141 and MANDYS142 has been characterised using a phage display pep tide library and a bacteriophage lambda cDNA library. Using a phage di splay library of random 15-mer peptides, the epitope recognised by the two antibodies was identified as EEXF. A lambda gtll clone obtained b y screening a human muscle cDNA library was shown to contain part of t he out-of-frame human mitochondrial succinyl CoA synthetase (alpha-sub unit) cDNA sequence which contains the sequence EEPL, suggesting a min imum requirement of EEXF/L for antibody binding. The sequence EEDF is located in the helical rod region of dystrophin and the N-terminal dom ain of alpha-actinin; this may explain why native dystrophin is not de tected, since the alpha-helical, coiled-coil folding of the rod region of dystrophin may obscure the epitope in the native protein. The anti body cross-reaction between dystrophin and alpha-actinin is likely to be fortuitous and not due to any structural homology that exists betwe en these two members of the spectrin superfamily.