Studies on the Attachment of Carbohydrate to Ovalbumin Nascent Chains in Hen Oviduct

We have examined the question, is the carbohydrate moiety of ovalbumin attached to nascent chains or to the completed protein after its release from polyribosomes. Ovalbumin nascent chains have been isolated from hen oviduct by immunoprecipitation of ovalbumin-synthesizing polysomes and subsequent isolation of peptidyl-tRNA by DEAE-cellulose chromatography. Our results indicate that both glucosamine and mannose are incorporated into ovalbumin nascent chains by hen oviduct fragments. Although the asparagine to which the carbohydrates are attached is 10 amino acid residues from the NH2 terminus, the majority of the carbohydrate, if not all, is attached only to those peptide chains that have been essentially completed.