Abstract
Binding of human growth hormone (hGH) to plasma membranes from rabbit liver is slightly
inhibited by β-mercaptoethanol (β-MSH), dithiothreitol (DTT), and N-ethylmaleimide
(NEM). L-Cys has a marked stimulating effect at 20 mM. Pretreatment of plasma membranes
with phospholipase A2-C, and D does not influence hGH binding. In the presence of DNase and RNase a slight
but distinct elevation of hormone binding is seen. HGH-receptor interaction is totally
abolished in the presence of trypsin. This effect is inhibited by trasylol and trypsin
inhibitor from soya bean. Neuraminidase has no effect on hGH binding, whereas α or
β-galactosidase lead to a complete abolition of hGH-receptor interaction. Analysis
of the receptor complex in the presence and absence of hGH leads to at least two distinct
polypeptide chains with molecular weights 68 000 and 76 000 daltons on the SDS-gel
electrophoresis. The significance of a peptide with 56 000 dalton is not clear. It
is concluded that -SH groups and phospholipids are not involved in hGH binding. The
effect of nucleases is not understood. Within the hormone recognition area peptide
chains carrying galactose residues in α and β-glycosidic bonding are essential for
hGH-receptor interaction. Two or three proteins seem to represent integral constituents
of the hGH receptor complex.
Key words
GH Receptor - Hormone Binding - Glycoprotein - Stereospecificity - Peptide Composition
1 Supported by a grant from the Deutsche Forschungsgemeinschaft Ko 457/7
2 European Prize Essay Paper of the German Endocrine Society, Marius-Tauk-Career Award
1979
