Immunoreactivity and receptor binding of mixed recombinants of human growth hormone and chorionic somatomammotropin

The behavior in six radioligand assays of the recombinant obtained by the noncovalent complementation of the reduced and carbamoylmethylated 134-residue amino-terminal fragment of human growth hormore with the reduced and carbamoylmethylated 51-residue carboxyl-terminal fragment of human chorionic somatomammotropin was compared to that of the analogous recombinant of the 133-residue amino-terminal fragment of human chorionic somatomammotropin and the 51-residue carboxyl-terminal fragment of human growth hormone. The determinants for the hepatic growth hormone receptor binding and for the lactogenic receptor binding of human growth hormone are on the amino-terminal fragments. The antigenic determinants for both a monospecific antiserum to human growth hormone and a monospecific antiserum to human chorionic somatomammotropin also are on the amino-terminal fragments of their respective antigens. The mixed recombinant of the amino-terminal fragment of human growth hormone with the carboxyl-terminal fragment of human chorionic somatomammotropin retains full radioimmuno- and radioreceptor activity after lyophilization.