Pattern of repeating aromatic residues in synexin. Similarity to the cytoplasmic domain of synaptophysin.

Synexin was isolated from bovine liver by high resolution cation exchange chromatography and fragmented with cyanogen bromide or trypsin. Peptides were isolated and their amino acid sequences partially determined. Twenty percent of the synexin sequence was determined in one contiguous sequence of 61 residues and a nonoverlapping sequence of 20 residues. The sequence is characterized by a hexapeptide repeat of the form YPXXXX occurring eight times in series, with phenylalanine substituting for tyrosine in two positions. The intervening amino acids (X) are predominantly proline, glycine and alanine. This pattern of periodic aromatic residues suggests the presence of a novel secondary structure and is similar to repeats present in synaptophysin, gliadin and type II keratin.