title: Localization of the steroid-binding site of the human sex steroid-binding protein of plasma (SBP or SHBG) by site-directed mutagenesis.
abstract: The amino-terminal region of the human sex steroid-binding protein of plasma (SBP or SHBG) containing K134 and M139 was found to represent part of the steroid-binding site. This was accomplished by constructing and expressing site-directed mutants having the following replacements: M139L, M139K, M139S, K134A, H235S, and Y57F. The results indicated that M139L and H235S were fully-active, K134A and Y57F were 50 and 67% active, M139K was 7% active, and M139S was inactive. These results support affinity-labeling data indicating that both K134 and M139 are located in or near the site, and suggest that Y57 may play a role in steroid binding. The fully active H235S mutant reveals that H235 is not involved in the steroid-binding process.
authors.affiliation: Department of Obstetrics and Gynecology, University of Washington, Seattle 98195.
authors.forename: L M
authors.initials: LM
authors.lastname: Sui
authors.forename: A W
authors.initials: AW
authors.lastname: Cheung
authors.forename: P C
authors.initials: PC
authors.lastname: Namkung
authors.forename: P H
authors.initials: PH
authors.lastname: Petra
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D004247:DNA; D004586:Electrophoresis; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D012738:Sex Hormone-Binding Globulin / Q000235:genetics / Q000378:metabolism*
chemical_list: D012738:Sex Hormone-Binding Globulin; D004247:DNA