Structure/function analyses of human sex hormone‐binding globulin by site‐directed mutagenesis
- 20 April 1992
- journal article
- Published by Wiley in FEBS Letters
- Vol. 301 (2) , 227-230
- https://doi.org/10.1016/0014-5793(92)81253-i
Abstract
Human sex hormone‐binding globulin (hSHBG) and rat androgen‐binding protein (rABP) exhibit distinct affinities for sex‐steroids. We therefore constructed and expressed a hSHBG/rABP hybrid cDNA encoding the N‐terminal portion of hSHBG (205 residues) and the C‐terminal portion of rABP (168 residues). The resulting chimera displayed similar steroid‐binding characteristics as hSHBG and was recognised by a monoclonal antibody (S1B5) for hSHBG. We then created substitutions at Ser‐133, His‐136 and Met‐139. The Asp‐133 and Gln‐136 mutants bound steroids in the same way as normal hSHBG while the steroid‐binding affinity of Trp‐139 was reduced. All three mutants cross‐reacted similarly in a hSHBG radioimmunoassay, but Gln‐136 was recognised poorly by the S1B5 antibody. These data imply that residues involved in steroid‐binding are located within the N‐terminal half of hSHBG and include Met‐139, and that the S1B5 epitope is located in this region.Keywords
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