Binding of native and reduced and carbamidomethylated hGH to rabbit liver plasma membranes.

Abstract

The binding properties of reduced and carbamidomethylated hGH (RCAM-hGH) were compared to those of native hGH. The time course of binding to rabbit liver plasma membranes and the response of binding to temperature of both RCAM-hGH and hGH were similar. RCAM-hGH binding exhibited a broad pH optimum for binding which was approximately 50% of the peak of hGH binding at pH 6. RCAM-hGH binding was not enhanced by divalent cations to the same extent as hGH binding, but monovalent cations affected the binding of both hormones similarly. The most striking difference in binding between RCAM-hGH and hGH was observed in the displacement curves of the hormones. Half-maximal displacement of 125I-hGH occurred at 19 and 38 pmoles⁄ml hGH and RCAM-hGH, respectively. In comparison, half-maximal displacement of 125IRCAM- hGH occurred at 26 and 46 pmoles⁄ml RCAM-hGH, respectively. Approximately 30–40% of l25I-RCAM-hGH was nondisplaceable by both RCAM-hGH and hGH compared to 10% for 125I-hGH. Scatchard plots of 125I-hGH bindi...