Time-dependent folding of immunological epitopes of the human chorionic gonadotropin beta-subunit.
We have explored the possibility to use 14 different monoclonal antibodies in order to follow the formation of the respective epitopes during the biosynthesis of hCG subunits and their association in JEG-3 choriocarcinoma cells using pulse (30s to 5 min)-chase (0-180 min) experiments. We found central cystine knot epitope structures (epitope beta1) to be formed immediately and simultaneously with epitopes on the protruding hCG-beta loops 1 and 3. We found also differences in the time-dependent folding of beta2 and beta4 epitopes, which are highly overlapping structures on the loops 1+3. These differences were reinforced by decreasing the temperature during the pulse-chase experiments to 25 degrees C. Moreover, we describe for the first time an intracellular intact hCG beta-subunit form that showed the transient expression of the hCG-beta-core fragment epitope beta11 in the course of the maturation of this subunit which casts new light on the presence of hCG-beta-core fragment in Down's syndrome, tumors and pregnancy.
Roig
J
J
Heidelberg University Biochemistry Center (BZH), Im Neuenheimer Feld 328, 69120 Heidelberg, Federal Republic of Germany.
Krause
J-M
JM
Berger
P
P
Merz
Wolfgang E
WE
D000911:Antibodies, Monoclonal / Q000276:immunology; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000737:chemistry* / Q000276:immunology* / Q000378:metabolism; D019281:Dimerization; D000939:Epitopes / Q000737:chemistry* / Q000276:immunology* / Q000378:metabolism; D015292:Glycoprotein Hormones, alpha Subunit / Q000737:chemistry / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D017510:Protein Folding; D011499:Protein Processing, Post-Translational; D021122:Protein Subunits / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D013997:Time Factors
D000911:Antibodies, Monoclonal; D018997:Chorionic Gonadotropin, beta Subunit, Human; D000939:Epitopes; D015292:Glycoprotein Hormones, alpha Subunit; D021122:Protein Subunits