Sequences of Sixteen Phosphoserine Peptides from Ovalbumins of Eight Species

Phosphoserine peptides have been isolated by a diagonal electrophoresis method from proteolytic digests of ovalbumins from hen, grouse, turkey, golden pheasant, magpie goose, chinese goose, Aylesbury duck and fulvous whistling duck. The amino acid sequences of these peptides have been determined. There are two sites of phosphorylation in each ovalbumin, which are located in two different regions of the ovalbumin molecule. Amino acid replacements are more frequent in the site 1 sequences than in the site 2 sequences. Both site 1 and site 2 sequences contain invariant residues. Sequence variations occur near the serine residues that are phosphorylated, but the amino acid two residues C-terminal to the phosphoserine is always glutamic acid, suggesting that this may be a recognition signal for the phosphorylating enzyme. Variations in amino acid sequence among the species are consistent with differences in the ovalbumins determined by peptide mapping and quantitative immunoprecipitation assays. A phylogenetic tree has been constructed from a comparison of the sequences of 248 residues from the eight ovalbumins.