Substitutions of tryptophan residues in human corticosteroid-binding globulin: impact on steroid binding and glycosylation.
Human corticosteroid-binding globulin (CBG) contains four tryptophan residues at positions 141, 185, 266 and 371; one of which is thought to be located in the steroid-binding site. These residues were substituted by site-directed mutagenesis and expression of mutant CBG cDNAs in Chinese hamster ovary cells. Analyses of the resulting mutants indicate that Trp371 is most likely located in the steroid-binding site, and that hydrophobic interactions between Trp141 and the steroid molecule or other amino-acids in the CBG polypeptide may also contribute to high-affinity interactions between CBG and its steroid ligands. In addition, substitution of Trp266 resulted in altered glycosylation of CBG, and this supports the concept that it participates in intra-molecular carbohydrate-polypeptide interactions which may influence the conformation and secretion of this glycoprotein.
Department of Obstetrics and Gynaecology, University of Western Ontario, London, Canada.
G V
GV
Avvakumov
G L
GL
Hammond
D001665:Binding Sites; D015153:Blotting, Western; D006031:Glycosylation; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013329:Structure-Activity Relationship; D014156:Transcortin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D014364:Tryptophan
D011994:Recombinant Proteins; D014364:Tryptophan; D014156:Transcortin; D006854:Hydrocortisone