Covalent structure of chicken pepsinogen

Chicken pepsinogen is a glycoprotein consisting of a single polypeptide chain and containing the following 367 amino acid residues: Asp23, Asn16, Thr26, Ser41, Glu14, Gln11, Pro18, Gly31, Ala17, Cys7, Val25, Met9, Ile23, Leu28, Tyr22, Phe20, His8, Lys17, Arg7, Trp4. The Mr‐value of the protein is 42074. This value includes the carbohydrate moiety of the protein, i.e. Man3, (GlcNAc)7, (‐SO3H)5. The primary fragmentation of the molecule was effected by limited trypsinolysis at arginine residues after preceding modification of the lysines with citraconic anhydride. All eight peptides expected in theory were obtained and their size, amino acid composition, and N‐terminal amino acid sequence were characterized. To elucidate the amino acid sequence of these large fragments the latter were subjected to secondary cleavage by CNBr, trypsin (after removal of the protecting groups from the lysines), the proteinase from Staphylococcus aureus V8 strain, α‐chymotrypsin, hydroxylamine, or dilute acid; the resulting peptides were isolated by gel permeation and ion‐exchange chromatography and by the fingerprint techniques. Overlaps at sites of the arginine residues were obtained in an earlier study