HISTOCHEMICAL DETECTION OF BINDING-SITES FOR HUMAN GROWTH-HORMONE USING BIOTINYLATED LIGAND

Recombinant human growth hormone was covalently linked to biotin via a six-carbon spacer arm. Biotinylation was confirmed by electrophoresis and mass spectrometry showed that approximately 50% of the hormone wa s monobiotinylated. The modified growth hormone (GH) was shown to bind to the GH receptor of IM9 human lymphoid cells with an affinity of 0. 55 x 10(9) M(-1). Bioactivity of biotinylated GH measured in the Nb2 b ioassay was 53.9% that of unlabeled GH. GH binding sites on human IM9 cells were visualized histochemically with the biotinylated hormone, a technique that provides a means of identifying receptors for GH on ta rget cells in vitro.