The primary structure of avian phosvitins. Contributions through the Edman degradation of methylmercaptovitins prepared from the constituent phosphoproteins.

Methylmercaptovitins were prepared from the constituent phosvitin phosphoproteins as well as from the CNBr cleavage peptides derived from the methionine-containing phosphoproteins. Edman degradation of these methylmercaptovitins has afforded partial sequence information and identifies the serine phosphorylation sites in the phosphoprotein. Primary structure, determined for approximately seventy-seven residues from the amino terminus of the hen methionine-containing phosphoprotein, agrees fully with that deduced from recently published nucleotide sequence data, and provides corrections to results of earlier work on enzymatically dephosphorylated samples. Partial sequence data, together with corrections to earlier results, are also provided for phosphoproteins from duck and turkey phosvitins, as well as for the methionine-free phosphoprotein from hen phosvitin. All phosphoproteins have N-terminal leader sequences of low serine content. Sequences of the methionine-containing group are homologous, as are the sequences of the methionine-free group, but the groups differ significantly from one another. Unphosphorylated sites appear to have a fractional distribution over all available serine residues.

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