The Limited Sequence Specificity of Anti-Peptide Antibodies may Introduce Ambiguity in Topological Studies

Abstract

Our present view of the membrane topology of nicotinic acetylcholine receptors (nAChR) heavily depends on hydropathy plots (Kyte kath Doolittle, 1982; Nöda et al., 1982; Claudio et al., 1983) and epitope mapping (Lindstrom et al., 1984; Maelicke et al., 1984; Neumann et al., 1984; Ratnam kath Lindstrom, 1984; Plümer et al., 1984; Young et al., 1985; Fuchs kath Safran, 1986; Ratnam et al., 1986a,b). The latter is usually performed with antibodies raised against rather long synthetic peptides. We have criticized this approach (Maelicke et al., 1984; Plümer et al., 1984) as it may lead to ambiguous results: Recent structural data have established that the antigen recognition site of antibodies is quite large and that antibody-antigen interaction probably involves multipoint attachment (Amit et al., 1986). Thus, only under limiting conditions will the charge density pattern defining an antibody binding site be directly correlated to the primary structure of this particular region of the antigen. The following results of a topological study of the nAChR from Torpedo electric organ (Maelicke et al., 1989) may exemplify this problem.