PMID: 7371643Apr 1, 1980Paper

On the number of steroid-binding sites of delta 5-3-oxosteroid isomerase

European Journal of Biochemistry
T M PenningP Talalay

Abstract

The number of steroid-binding sites in delta 5-3-oxosteroid isomerase of Pseudomonas testosteroni (EC 5.3.3.1) has been determined from measurements of the red shift of the ultraviolet chromophore of 19-nortestosterone upon binding to the enzyme. The experiments include spectroscopic measurements when limiting concentrations of either 19-nortestosterone or isomerase are titrated with varying concentrations of the complementary ligand. Analysis of the results indicates one binding site per subunit (Mr 13 394). Scatchard plots indicate a single family of equivalent binding sites. 5, 10-Secoestr-5-yne-3, 10, 17-trione is a suicide substrate of isomerase [Batzold & Robinson (1975) J. Am. Chem. Soc. 97, 2576]. The time course for inactivation of isomerase with an excess of 5, 10-seco[7-3H]estr-5-yne-3, 10, 17-trione was parallel to the covalent incorporation of steroid and gave a final stoichiometry of nearly one steroid molecule per subunit of enzyme. Alkylation of [14C] isomerase with excess of this 3H-labeled steroid followed by gel-filtration and dialysis gave an inactivated enzyme with a 3H/14C ratio that corresponds to one molecule of steroid bound per subunit; this stoichiometry was constant over a wide range of protein conce...Continue Reading

References

Jan 1, 1976·Advances in Enzyme Regulation·F H BatzoldP Talalay
Aug 4, 1976·Journal of the American Chemical Society·D F Covey, C H Robinson
Apr 30, 1975·Journal of the American Chemical Society·F H Batzold, C H Robinson
Sep 1, 1975·The Biochemical Journal·G L Atkins, I A Nimmo
Jan 23, 1976·The Journal of Organic Chemistry·F H Batzold, C H Robinson
Feb 15, 1976·FEBS Letters·F VincentE E Baulieu
Feb 5, 1974·Journal of Molecular Biology·J Schlessinger, A Levitzki
May 29, 1974·Biochimica Et Biophysica Acta·A M BensonP Talalay
Jun 1, 1974·The Biochemical Journal·R Eisenthal, A Cornish-Bowden
Oct 1, 1955·Biochimica Et Biophysica Acta·P TALALAY, V S WANG
Aug 1, 1961·The Biochemical Journal·G N WILKINSON

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