Location of major antigenic sites of the beta subunit of human chorionic gonadotropin.
Purified beta subunit of human chorionic gonadotropin (hCG) was partially reduced with beta-mercaptoethanol, carboxymethylated, and digested with chymotrypsin. The peptides were isolated by high-voltage electrophoresis and paper chromatography. Five major disulfide-containing peptides were isolated, and their location in the parent molecule was established by amino acid composition and amino- and carboxy-terminal analyses. All of these peptides inhibited the binding of 125I-labeled hCG by anti-beta hCG serum. The inhibitory effect of these peptides was lost when their disulfide bonds were reduced and alkylated. Synthetic carboxy-terminal peptides were not inhibitory. Based on these data it is concluded that a major antigenic site of hCG resides in the region of residues 21-23 with a disulfide bond connecting cysteine-23 or -26 with the cysteines at positions 72 or 110.
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D006063:Chorionic Gonadotropin / Q000276:immunology; D002918:Chymotrypsin; D004220:Disulfides / Q000032:analysis; D000939:Epitopes; D006801:Humans; D046911:Macromolecular Substances; D010446:Peptide Fragments / Q000032:analysis; D011863:Radioimmunoassay
D000596:Amino Acids; D006063:Chorionic Gonadotropin; D004220:Disulfides; D000939:Epitopes; D046911:Macromolecular Substances; D010446:Peptide Fragments; D002918:Chymotrypsin