Steroid-Protein Interactions

I. Introduction.- II. Early Studies on Interactions between Proteins and Small Molecules or Ions.- III. First Observations on Reversible Binding of Steroids to Proteins.- IV. Basic Methods for Determination of Steroid-Protein Interactions.- 1. General Principles.- 2. Measurement of Biological Activity.- 3. Ultrafiltration.- 4. Electrophoresis.- 5. Equilibrium Dialysis.- 6. Solvent Extraction.- 7. Measurement of Solubility.- 8. Turbidimetry.- 9. Solvent Partition.- 10. Ultracentrifugation.- 11. Paper Chromatography.- 12. Equilibrium Fractionation.- 13. Spectrophotometry.- 14. Gel Filtration.- 15. Gel Equilibration.- 16. Use of Radiolabeled Steroids and the Problem of Decomposition.- V. Characteristics of Steroid-Protein Interactions.- 1. Molecular Characteristics of Steroids.- 2. Molecular Aspects of the Interaction.- 3. Some Pertinent Questions.- 4. Presentation of Binding Data.- a) General Considerations.- b) The Logarithmic Plot.- c) The Reciprocal Plot.- d) The Scatchard Plot.- e) Approximate Free Energy, Enthalpy and Entropy.- f) Competition between Different Steroids for the Same Binding Site.- g) Calculation of Distribution of a Steroid between Two Binding Proteins.- VI. Steroid Interactions with Serum Proteins Other than Specific Glycoproteins.- 1. Interactions of Bile Acids.- 2. Interactions of Steroid Conjugates.- 3. Interaction of Monopolar Neutral Steroids; Lipoproteins.- 4. Interactions of Duo- and Polypolar Neutral Steroids Qualitative Observations with Steroid Hormones.- 5. Steroid Interaction with Serum Albumin.- a) Experimental Data.- b) Quality of Albumin.- c) Binding Parameters.- d) Influence of Albumin Concentration.- e) Influence of Temperature.- f) Influence of pH and Ionic Strength.- g) Competition between Steroids in HSA Interaction.- VII. Influence of Molecular Structure on Steroid Interaction with HSA and Other Proteins.- 1. Steroid Structure and Binding to Serum Albumin; Polarity Rule.- 2. Steric Considerations.- 3. Protein Structure in Relation to Steroid Interaction.- 4. Spectral Observations on Steroid Interaction with Compounds Other than Proteins.- VIII. Corticosteroid-Binding Globulin (CBG) of Man and Other Species.- 1. Fundamental Observations.- 2. Methods of Measurement.- a) Equilibrium Dialysis and Related Techniques.- b) CBG in Competitive Binding Analysis: Quantification of Binding Sites and of Steroids.- c) Gel Filtration.- 3. Removal of Endogenous Steroid from Serum.- 4. General Properties of CBG in Serum.- a) Influence of Temperature on Binding Affinity.- b) Influence of pH on Binding Affinity.- c) Electrophoretic Characteristics.- 5. CBG Activity in Human Plasma or Serum.- a) Concentration of Binding Sites and Association Constants of Human CBG.- b) CBG Concentration in Humans Under Conditions Other than Normal.- ?) Hereditary Familial Decrease of CBG Level.- ?) CBG Level in Pregnancy and after Estrogen Administration.- ?) CBG Level in Pathological States.- 6. CBG Activity in Species Other than Human.- IX. Influence of Various Endogenous Factors on CBG Activity in the Rat.- 1. Initial Observations; Effect of Adrenalectomy.- 2. General Procedures Used in the Endocrine-Related Studies.- 3. Influence of Age and Sex on CBG Activity and Corticosterone Level.- 4. Influence of Gonadal Hormones.- a) Effects of Gonadectomy.- b) Injection of Steroid Sex Hormones.- 5. CBG Activity during Estrous Cycle, Pregnancy, Lactation and Weaning.- 6. Significance of the Pituitary Gland for CBG Activity.- 7. Recognition of the Thyroid-Stimulating Hormone as the CBG-Controlling Factor.- 8. Further Interrelation of Endocrine Effects on CBG Activity in the Rat.- 9. Summary and Conclusions.- X. CBG Activity in Mouse, Rabbit and Guinea Pig during Pregnancy and Lactation; PBG in the Guinea Pig.- 1. Observations on the Steroid Binding Activities.- 2. Identification of PBG in the Guinea Pig.- 3. Interpretation of the Possible Role of CBG.- XI. Isolation and Properties of CBG from Mammalian Sera.- 1. Isolation of Human CBG.- 2. Isolation of Rabbit and Rat CBG.- 3. Physicochemical Characterization.- 4. Steroid Binding Parameters.- 5. Observations on Polymerization of Rat CBG.- XII. High-Affinity Binding of Estradiol and Testosterone to Serum Proteins.- 1. Binding of Estrogens.- 2. Binding of Testosterone.- 3. Steroid-Binding ?-Globulin.- XIII. Interaction of Progesterone and Other Steroids with ?1-Acid Glycoprotein (AAG).- 1. General Properties of the Progesterone-AAG Complex; Relation to CBG Binding.- 2. Reversible Inhibition by Lipid of the Binding Affinity between AAG and Progesterone.- 3. Reversible Inhibition by Heavy Metal Ions of the Binding Affinity between AAG and Progesterone.- 4. Interaction of Other Steroids with AAG.- 5. Influence of Perturbants on Steroid-AAG Interactions.- 6. Chemical Modification of AAG in Relation to Steroid Binding.- XIV. Effect of Protein Binding on Hormonal Activity of Steroids.- 1. Corticosteroid Hormones.- 2. Progesterone.- XV. Steroid-Binding Immunoglobulins: Preparation, Properties, and Application for Radioiinmunoassay of Steroid Hormones.- XVI. Notes on Steroid Interactions with Enzymes.- XVII. Synopsis.- A. List of Abbreviations and Symbols.- B. Calculation of Average Hydrophobicities and of Non-polar Side Chain Frequencies.