Sequence similarity between epidermal growth factor precursor and atrial natriuretic factor precursor

Computer-assisted analysis for homology of the EGF precursor revealed the presence of two large duplication units, each comprising 5 non-EGF-like homologous segments each of about 40 residues length and 3 or 4 EGF-like segments. The amino acid sequences of the non-EGF-like repeats were subjected to search for homology with 2600 known protein sequences compiled in our database. An unexpected but statistically significant homology has been found, when compared with the atrial natriuretic factor precursor. The functional and evolutionary implications of the homology observed between the two different precursors are also discussed.