Species- and Subtype-Specific Recognition by Antibody WF6 of a Sequence Segment Forming an α-Bungarotoxin Binding Site on the Nicotinic Acetylcholine Receptor α Subunit

The monoclonal antibody WF6 competes with acetylcholine and alpha-bungarotoxin (alpha-BGT) for binding to the Torpedo nicotinic acetylcholine receptor (nAChR) alpha-1 subunit. Using synthetic peptides corresponding to the complete Torpedo nAChR alpha-1 subunit, we previously mapped a continuous epitope recognized by WF6, and the prototope for alpha-BGT, to the sequence segment alpha-1(181-200). Single amino acid substitution analogs have been used as an initial approach to determine the critical amino acids for WF6 and alpha-BGT binding. In the present study, we continue our analysis of the structural features of the WF6 epitope by comparing its cross-reactivity with synthetic peptides corresponding to the alpha-1 subunits from the muscle nAChRs of different species, the rat brain alpha-2, alpha-3, alpha-4 and alpha-5 nAChR subtypes, and the chick brain alpha-BGT binding protein subunits, alpha-BGTBP alpha-1 and alpha-BGTBP alpha-2. Our results indicate that WF6 is able to cross-react with the muscle alpha-1 subunits of different species by virtue of conservation of several critical amino acid residues between positions 190-198 of the alpha-1 subunit. These studies further define the essential structural features of the sequence segment alpha-1(181-200) required to form the epitope for WF6.