Development of laminin receptor agonists: identification of important functional residues by alanine scanning

An antagonist of cellular adhesion and motility, acetyl-C-[S-Acm]-VIGYSGDRC -[S-Acm]-NH2 (mEGF((33-42))), shares homology with the agonist sequence CDP GYIGSR-NH2. It has been proposed that the latter peptide binds to the high affinity 67 kDa laminin receptor. Both peptides have equal affinities for t he receptor and similar conformations have been derived for both. We have e xamined the importance of individual non-homologous residues with respect t o receptor binding and antagonistic properties of mEGF((33-42)). Alanine sc anning of non-conserved residues in the N-terminal half of mEGF(33-42) caus ed loss of biological activity with respect to cell attachment, receptor bi nding and migratory response. Substitution of alanine for serine (position 6) caused loss of laminin-specific cell attachment and receptor binding act ivities. However, the peptide did stimulate migration suggesting that this peptide may be a non-specific stimulator of migration. In contrast, alanine substitution for the C-terminal Cys-S-Acm had no apparent effect on the at tachment or receptor binding activities of the peptide but generated an ago nist from the antagonist parent. Comparison of the modelled folds of the al anine containing peptides revealed the presence of significant helical cont ent in those peptides capable of stimulating migration and suggests that a reduction in bulk in the N-terminal residues is not conducive to adopting a productive binding conformation. (C) 2000 Elsevier Science B.V. All rights reserved.