Abstract
Molecular co-evolution is a key feature of biological systems. Molecular interactions (ligand-receptor, protein-protein, etc.) usually evolve simultaneously and independently to optimize binding. Frequently, these interactions involve one receptor that binds multiple ligands. Each ligand often leads to a different pathway activation intra-cellularly. Understanding single amino acid roles in evolving ligands and their contributions to downstream pathways of the receptor is still challenging.
We developed a cross-conservation approach to identify functionally important EGF residues. Four EGF mutants (N32R, D46R, K48T, W50Y) have been selected and studied biochemically and at the cellular level. While these mutants retain binding affinities for EGFR similar to that of EGF, surprisingly the effects of two of them (D46R, K48T) at the cellular level changed, inducing higher proliferation levels in normal fibroblasts and reducing proliferation in skin cancer cells. These results lay the base to understand the basis of EGF signaling.