Structure/function analyses of human sex hormone-binding globulin: effects of zinc on steroid-binding specificity.

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Hammond GL, Avvakumov GV, Muller YA

Structure/function analyses of human sex hormone-binding globulin: effects of zinc on steroid-binding specificity.

J Steroid Biochem Mol Biol. 2003 Jun;85(2-5):195-200. doi: 10.1016/s0960-0760(03)00195-x.

PubMed ID

12943704 [ View in PubMed

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Abstract

In humans, sex hormone-binding globulin (SHBG) binds and transports the biologically most important androgens and estrogens in the blood, and regulates the access of these steroids to their targets tissues. In addition to binding sex steroids, SHBG has specific binding sites for divalent cations including calcium and zinc. Zinc binding to a site at the entrance of the steroid-binding pocket in human SHBG has been shown to reduce its affinity for estrogens, while having no impact on the binding of C19 steroids. Crystallographic studies indicate that C18 and C19 steroids are bound in opposite orientations within the SHBG steroid-binding site, and we have obtained new information that supports a molecular model explaining the mechanism by which zinc alters the affinity of human SHBG for estrogens, by studying directly the estradiol-binding properties SHBG variants created by site-directed mutagenesis. In this model, the coordination of a zinc ion by the side chains of residues Asp65 and His136 eliminates a critical hydrogen bond between Asp65 and the hydroxyl at C3 of estrogens, such as estradiol and 2-methoxyestradiol, and causes disorder in a polypeptide loop segment that covers the steroid-binding site. The combination of these structural changes explains the specific decrease in the affinity of human SHBG for C18 steroids in the presence of a zinc ion.

DrugBank Data that Cites this Article

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Zinc chloride	Corticosteroid-binding globulin	Protein	Humans	Unknown	Modulator	Details
Zinc chloride	Sex hormone-binding globulin	Protein	Humans	Unknown	Modulator	Details
Zinc sulfate, unspecified form	Corticosteroid-binding globulin	Protein	Humans	Unknown	Modulator	Details
Zinc sulfate, unspecified form	Sex hormone-binding globulin	Protein	Humans	Unknown	Modulator	Details