Identification of the cysteine in the steroid-binding site of human corticosteroid binding globulin by site-directed mutagenesis and site-specific chemical modification. 1994

J Ghose-Dastidar, and R Green, and J B Ross
Department of Biochemistry, Mount Sinai School of Medicine, New York, NY 10029-6574.

Binding of corticosteroids by human corticosteroid binding globulin (hCBG) is thought to involve interaction with one of its two cysteine residues (Cys60 and Cys228). To identify which of the two cysteine residues mediates steroid binding, we have produced mutant hCBGs containing serine or alanine in place of Cys228 by site-directed mutagenesis. Alteration of Cys228 to serine or alanine does not change the steroid binding affinity of hCBG, demonstrating that Cys228 is not involved in the binding interaction. This finding strongly suggests that Cys60 is the functionally important cysteine. By modifying the wild-type and mutant hCBGs with the sulfhydryl-specific reagents N-ethylmaleimide, iodoacetamide, and sodium tetrathionate, we have demonstrated that Cys60 is present at the steroid binding site, and that it may be directly involved in steroid binding. This result also identifies Cys60 as the accessible cysteine reported in previous studies.

UI MeSH Term Description Entries
D008969 Molecular Sequence Data Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories. Sequence Data, Molecular,Molecular Sequencing Data,Data, Molecular Sequence,Data, Molecular Sequencing,Sequencing Data, Molecular
D009154 Mutation Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations. Mutations
D003545 Cysteine A thiol-containing non-essential amino acid that is oxidized to form CYSTINE. Cysteine Hydrochloride,Half-Cystine,L-Cysteine,Zinc Cysteinate,Half Cystine,L Cysteine
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D001483 Base Sequence The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence. DNA Sequence,Nucleotide Sequence,RNA Sequence,DNA Sequences,Base Sequences,Nucleotide Sequences,RNA Sequences,Sequence, Base,Sequence, DNA,Sequence, Nucleotide,Sequence, RNA,Sequences, Base,Sequences, DNA,Sequences, Nucleotide,Sequences, RNA
D001665 Binding Sites The parts of a macromolecule that directly participate in its specific combination with another molecule. Combining Site,Binding Site,Combining Sites,Site, Binding,Site, Combining,Sites, Binding,Sites, Combining
D013256 Steroids A group of polycyclic compounds closely related biochemically to TERPENES. They include cholesterol, numerous hormones, precursors of certain vitamins, bile acids, alcohols (STEROLS), and certain natural drugs and poisons. Steroids have a common nucleus, a fused, reduced 17-carbon atom ring system, cyclopentanoperhydrophenanthrene. Most steroids also have two methyl groups and an aliphatic side-chain attached to the nucleus. (From Hawley's Condensed Chemical Dictionary, 11th ed) Steroid,Catatoxic Steroids,Steroids, Catatoxic
D013439 Sulfhydryl Reagents Chemical agents that react with SH groups. This is a chemically diverse group that is used for a variety of purposes. Among these are enzyme inhibition, enzyme reactivation or protection, and labelling. SH-Reagents,Sulfhydryl Compound Antagonists,Sulfhydryl Compound Inhibitors,Thiol Reagents,Sulfhydryl Compounds Antagonists,Sulfhydryl Compounds Inhibitors,Antagonists, Sulfhydryl Compound,Antagonists, Sulfhydryl Compounds,Compound Antagonists, Sulfhydryl,Compound Inhibitors, Sulfhydryl,Inhibitors, Sulfhydryl Compound,Inhibitors, Sulfhydryl Compounds,Reagents, Sulfhydryl,Reagents, Thiol,SH Reagents
D014156 Transcortin A serpin family member that binds to and transports GLUCOCORTICOIDS in the BLOOD. Corticosteroid-Binding Globulin,Serpin A6,Corticosteroid Binding Globulin
D016297 Mutagenesis, Site-Directed Genetically engineered MUTAGENESIS at a specific site in the DNA molecule that introduces a base substitution, or an insertion or deletion. Mutagenesis, Oligonucleotide-Directed,Mutagenesis, Site-Specific,Oligonucleotide-Directed Mutagenesis,Site-Directed Mutagenesis,Site-Specific Mutagenesis,Mutageneses, Oligonucleotide-Directed,Mutageneses, Site-Directed,Mutageneses, Site-Specific,Mutagenesis, Oligonucleotide Directed,Mutagenesis, Site Directed,Mutagenesis, Site Specific,Oligonucleotide Directed Mutagenesis,Oligonucleotide-Directed Mutageneses,Site Directed Mutagenesis,Site Specific Mutagenesis,Site-Directed Mutageneses,Site-Specific Mutageneses

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