Selenomethionyl analog of recombinant human choriogonadotropin

Selenomethionyl and high mannose type analog of recombinant human choriogonadotropin (hCG) to solve the crystallization and phase problems has been obtained by gene transfer methodology. SF9 insect cells were infected with the recombinant viruses containing hCG alpha and hCG beta cDNAs in selenomethionine containing methionine-free Grace's medium. The selenomethionyl hCG (SehCG) was purified from the culture medium by one step immunoaffinity chromatography using an immobilized monoclonal antibody against hCG beta. The presence of selenomethionine was demonstrated by amino acid analysis of SehCG. The amino acid composition indicated that more than 84% of methionine residues were substituted by selenomethionine. Its sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis yielded a single 38-kDa protein band under nonreducing conditions. The carbohydrate analysis of SehCG was consistent with the presence of four N-linked high mannose type carbohydrates and four O-linked simple disaccharide chains. The in vitro immunological and biological studies of SehCG indicated that selenomethionine substitution had no effect on the immunopotency, receptor binding, and steroidogenic activities of the hormone.