MAPPING OF ASSEMBLED EPITOPIC REGIONS OF HUMAN CHORIONIC-GONADOTROPINREVEALS PROXIMITY OF CTP-ALPHA TO THE DETERMINANT LOOP BETA-93-100

Three overlapping assembled epitopes of beta hCG have been mapped usin g MAb probes and a single step solid phase radioimmunoassay. These epi topes have been shown to be at receptor binding region comprising of t he loop region beta Cys93-Cys100. Importance of disulphide bonds in ma intaining integrity of these epitopes is assessed. Two MAbs (INN 58 an d INN 22) interact with the beta region as well as the alpha C-termina l peptide, while the other MAb INN 24 interacts with only the beta reg ion. Cross-reactivity pattern with beta hCG and hLH as web as the repo rted crystal structure of hCG substantiates the epitope identification . The results demonstrate utility of MAbs as probes in investigations on three-dimensional structure of gonadatropins.