Reports

Dimerization of human growth hormone by zinc

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Science  02 Aug 1991:
Vol. 253, Issue 5019, pp. 545-548
DOI: 10.1126/science.1907025

Abstract

Size-exclusion chromatography and sedimentation equilbrium studies demonstrated that zinc ion (Zn2+) induced the dimerization of human growth hormone (hGH). Scatchard analysis of 65Zn2+ binding to hGH showed that two Zn2+ ions associate per dimer of hGH in a cooperative fashion. Cobalt (II) can substitute for Zn2+ in the hormone dimer and gives a visible spectrum characteristic of cobalt coordinated in a tetrahedral fashion by oxygen- and nitrogen-containing ligands. Replacement of potential Zn2+ ligands (His18, His21, and Glu174) in hGH with alanine weakened both Zn2+ binding and hGH dimer formation. The Zn(2+)-hGH dimer was more stable than monomeric hGH to denaturation in guanidine-HCl. Formation of a Zn(2+)-hGH dimeric complex may be important for storage of hGH in secretory granules.