Sequential comparison of peptides containing half-cystine residues from ovalbumins of six avian species
Sun. Y. (Kagawa Univ., Takamatsu (Japan).) | Hayakawa, S.
Hen ovalbumin contains one cystine disulfide (Cys sub(73)-Cys sub(120)) and four cysteine sulfhydryl groups (Cys sub(11), Cys sub(30), Cys sub(367), and Cys sub(382)) in a single polypeptide chain of 385 amino acid residues. To investigate whether or not such a structure is shared by related avian species, the contents of disulfide-involved half-cystine residues and their positions in the primary structure of ovalbumins from five species were compared with those of hen ovalbumin. Ovalbumins were alkylated with a fluorescent dye, IAEDANS, under disulfide-reduced and disulfide-intact conditions and digested with a number of proteolytic enzymes. The sequences were deduced from peptides containing half-cystine residues labeled with the fluorescent dye. The results showed that the number of free cysteine sulfhydryl groups of ovalbumins was different among the species, three for guinea fowl and turkey (Cys sub(11), Cys sub(367), and Cys sub(382)); and two for Pekin duck, mallard duck, and Emden goose (Cys sub(11) and Cys sub(331)). On the other hand, a single intrachain disulfide bond could be identified from ovalbumins of five species using a combination of peptide mapping and N-terminal amino acid sequencing analysis under reduced and nonreduced conditions, in which the intrachain disulfide bond was like that of hen ovalbumin (Cys sub(73)-Cys sub(120)). The results also indicated that the variations in amino acid sequences on these peptides containing half-cystine residues bear a close relationship with the phylogeny of the six species.
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