Covalent Structure of a Low-Molecular-Mass Protein, Meleagrin, Present in a Turkey (Meleagris gallopavo) Ovomucoid Preparation

Abstract

A low-molecular-mass protein, tentatively named meleagrin, was isolated from a commer-cial preparation of turkey (Meleagris gallopavo) ovomucoid. This 40-amino acid protein contains 3 disulfide bonds and high concentrations of aromatic residues (2 tryptophans and 3 tyrosines). It lacks threonine, methionine, phenylalanine, and arginine residues. The complete amino acid sequence was determined to be the following: <Glu-Val-Len-Lys-Tyr-Cys-Pro-Lys-Ile-Gly-Tyr-Cys-Ser-Ser-Lys-Cys-Ser-Lys- Ala-Glu-Val-Trp-Ala-Tyr-Ser-Pro-Asp-Cys-Lys-Val-His-Cys-Cys-Val-Pro-Ala-Asn-Gln-Lys-Trp. One of the three disulfide bonds exists between Cys¹² and Cys²⁸, and the two others links Cys³²-Cys³³ with Cys6 and Cys16. The amino acid sequence of meleagrin shows a strong homology to a similar basic protein, cygnin (Simpson, G. R. & Morgan, F. J. [1983] Int. J. Pep. Protein Res. 22, 476-481), of a rather distantly related ayes, black swan (Cygnus atratus), suggesting some vital role of this protein in avian eggs. Similarity to a part (exon 9) of transferrins was also recognized.