Characterization of a cleavage product in the human choriogonadotropin beta-subunit.
The various molecular forms of human chorionic gonadotropin present in a crude preparation of urine from pregnant women were analyzed by two-dimensional gel electrophoresis and immunoblotting with monoclonal antibodies directed to synthetic peptides corresponding to the carboxyl-terminal part of either the alpha or beta-subunit. Under reducing conditions, immunoblotting with antibodies directed to the beta-subunit revealed the presence of a low-molecular-weight material of 22 kDa. This molecular form had large heterogeneity, as analyzed by isoelectrofocusing; it was immunoreactive with antibodies directed to the 111-145 region. Using microsequencing techniques, we found that the fragment had a NH2 terminal portion corresponding to the sequence of the beta-subunit appearing from residue 48. Thus, the 22-kDa fragment comprises the 48-145 portion of the beta-subunit and is probably a cleavage product of the native protein with intrachain nicking.
Bidart
J M
JM
Unité de Biochimie Clinique, Institut Gustave, Roussy, Villejuif, France.
Puisieux
A
A
Troalen
F
F
Foglietti
M J
MJ
Bohuon
C
C
Bellet
D
D
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal; D006063:Chorionic Gonadotropin / Q000032:analysis*; D018997:Chorionic Gonadotropin, beta Subunit, Human; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006801:Humans; D007986:Luteinizing Hormone / Q000032:analysis; D010446:Peptide Fragments / Q000032:analysis*; D011247:Pregnancy
D000911:Antibodies, Monoclonal; D006063:Chorionic Gonadotropin; D018997:Chorionic Gonadotropin, beta Subunit, Human; D010446:Peptide Fragments; D007986:Luteinizing Hormone