Alanine scanning of MAP2 (a) and MAP3 (b) sequences. Twelve different tetra-branched MAPs, each carrying a single alanine substitution in the lead sequence, were tested for inhibition of PA63–LF binding by ELISA and compared with the activity of corresponding lead sequence in the same experiment. Results are means±S.D. for at least three experiments. (c) Summary of inhibitory activity of MAPs derived from progressive shortening of MAP2 (left-hand panel) and MAP3 (right-hand panel) sequences on PA63–LF binding in ELISA. Results are from at least three experiments for each peptide. Black squares, MAP inhibitory activity was more than 65% that of the lead MAP tested under the same conditions; grey squares, peptide activity was between 65 and 35% that of the lead MAP; white squares, peptide had less than 35% of the inhibitory activity of the lead peptide.