Characterization of the binding of thyroxine to high density lipoproteins and apolipoproteins A-I

The Journal of Clinical Endocrinology and Metabolism
S BenvengaJ Robbins

Abstract

We studied binding of T4 to the lipid-complexed apolipoproteins (apo) of high density lipoproteins (HDL), the major lipoprotein carrier of thyroid hormones in human plasma, and to lipid-free apoA-I. HDL isolated from fresh normal plasma by ultracentrifugation (density, 1.063-1.210 g/mL) was photoaffinity labeled with [3,5-(125)I]T4 and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Two bands corresponding to apoA-I (28.3K) and apoC-II or apoC-III (8.6-9.2K) were seen, and their radioactivity decreased by 50-60% when labeled in the presence of 1 mumol/L T4. Photoaffinity labeling of isolated apoA-I also was demonstrated and was decreased 74% by 1 mumol/L T4, suggesting a higher affinity of the lipid-free protein for T4. T4 binding of isolated apoA-I was optimal at pH 7-8, reached a maximum after 1 h at 23 C, and decreased after incubation at 37 C. Scatchard analysis revealed a single T4-binding site with a Ka of 7.5 x 10(7) L/mol at 23 C, pH 8.2. The potency of T4 analogs as inhibitors of T4 binding to isolated apoA-I was L-T4 = D-T4 = triiodothyroacetic acid = L-rT3 much greater than L-T3 much greater than L-thyronine. The binding of T4 to apoA-I was reduced by known inhibitors of T4 binding to serum pro...Continue Reading

Citations

Aug 24, 2002·Thyroid : Official Journal of the American Thyroid Association·Salvatore BenvengaFrancesco Trimarchi
Jan 1, 1994·Thyroid : Official Journal of the American Thyroid Association·S BenvengaJ Robbins
Mar 9, 2002·Journal of Endocrinological Investigation·S BenvengaF Trimarchi
Dec 13, 1963·Biochimica Et Biophysica Acta·K TOIH J CAHNMANN
Mar 22, 2013·Journal of Lipid Research·Kasey C Vickers, Alan T Remaley
Feb 11, 2020·Frontiers in Pharmacology·Nik Nur Syazana Binti Nik Mohamed Kamal, Wan Nazatul Shima Shahidan
May 1, 1992·The American Journal of Physiology·P J Babin
Feb 9, 1993·Biochemical Pharmacology·A N HannaH A Newman

❮ Previous
Next ❯

Related Concepts

Related Feeds

ApoE, Lipids & Cholesterol

Serum cholesterol, triglycerides, apolipoprotein B (APOB)-containing lipoproteins (very low-density lipoprotein (VLDL), immediate-density lipoprotein (IDL), and low-density lipoprotein (LDL), lipoprotein A (LPA)) and the total cholesterol/high-density lipoprotein (HDL) cholesterol ratio are all connected in diseases. Here is the latest research.