Effect of mutations in the β1‐thyroid hormone receptor on the inhibition of T3 binding by desethylamiodarone

FEBS Letters

Wiersinga, W.M.¹  Chatterjee, V.K.K.²  Bakker, O.¹  van Beeren, H.C.¹ 

[1]Department of Endocrinology, Academic Medical Centre F5-171, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands

[2]Department of Medicine, University of Cambridge, Level 5 Addenbrooke's Hospital, Hills Road, Cambridge CB2 2QQ, UK

关键词: Desethylamiodarone;    Mutant β1-thyroid hormone receptor;    Inhibition of triiodothyronine binding;   

DOI  :  10.1016/S0014-5793(99)00453-6

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Desethylamiodarone (DEA) acts as a competitive inhibitor of triiodothyronine (T₃) binding to the α₁-thyroid hormone receptor (TRα₁) but as a non-competitive inhibitor with respect to TRβ₁. To gain insight into the position of the binding site of desethylamiodarone on TRβ₁ we investigated the naturally occurring mutants Y321C, R429Q, P453A, P453T and the artificial mutants L421R and E457A in the ligand binding domain of human TRβ₁. The IC₅₀ values (in μM) of DEA for P453A (50±11) and P453T (55±16) mutant TRβ₁ are not different from that for the wild type TRβ₁ (56±15), but the IC₅₀ values of R429Q (32±7; P<0.001) and E457A (17±3; P<0.001) are significantly lower than of the wild type. Scatchard plots and Langmuir analyses indicate a non-competitive nature of the inhibition by DEA of T₃ binding to all four mutant TRβ₁s tested. Mutants P453A and P453T do not influence overall electrostatic potential, and also do not influence the affinity for DEA compared to wild type. Mutant E457A causes a change from a negatively charged amino acid to a hydrophobic amino acid, enhancing the affinity for DEA. Mutant R429Q, located in helix 11, causes an electrostatic potential change from positive to uncharged, also resulting in greater affinity for DEA. We therefore postulate that amino acids R429 and E457 are at or close to the binding site for DEA, and that DEA does not bind in the T₃ binding pocket itself, in line with the non-competitive nature of the inhibition of T₃ binding to TRβ₁ by DEA.

【 授权许可】

Unknown