TY - JOUR
T1 - Leucine at codon 428 in the ninth heptad of thyroid hormone receptor β1 is necessary for interactions with the transcriptional cofactors and functions regardless of dimer formations
AU - Monden, Tsuyoshi
AU - Yamada, Masanobu
AU - Ishii, Sumiyasu
AU - Hosoya, Takeshi
AU - Satoh, Teturo
AU - Wondisford, Fredric E.
AU - Hollenberg, Anthony N.
AU - Mori, Masatomo
PY - 2003/5/1
Y1 - 2003/5/1
N2 - Structure/function studies of the thyroid hormone receptor (TR) β1 have demonstrated that single amino acid substitutions in either position 428 or 429 in the ligand-binding domain (LBD) can alter heterodimerizations and homodimerizations, respectively. A leucine at 428 is located in a highly conserved region corresponding to the putative ninth heptad repeat of a leucine-zipper-like motif in the LBD of TRβ1. To investigate how the side chain of amino acids at 428 affect receptor characteristics, gel-shift mobility shift assays and yeast two-hybrid assays were analyzed. The neutral status amino acids such as a leucine (wild-type) or a glutamine at 428 preferred heterodimerization with RXR. Furthermore, a positively charged side chain of amino acids at 428 such as an arginine or a lysine, preserved homodimer formation. Irrespective of charge, ninth heptad mutant receptors did not bind the ligand and were not able to interact with either corepressor or coactivating proteins. Limited trypsinization assays revealed no major conformational change in the ninth heptad mutant receptors. Together, these findings suggested that a leucine at 428 was a critical amino acid for both interaction with the thyroid hormone receptor associated proteins and ligand-independent and -dependent functions regardless of dimer formations.
AB - Structure/function studies of the thyroid hormone receptor (TR) β1 have demonstrated that single amino acid substitutions in either position 428 or 429 in the ligand-binding domain (LBD) can alter heterodimerizations and homodimerizations, respectively. A leucine at 428 is located in a highly conserved region corresponding to the putative ninth heptad repeat of a leucine-zipper-like motif in the LBD of TRβ1. To investigate how the side chain of amino acids at 428 affect receptor characteristics, gel-shift mobility shift assays and yeast two-hybrid assays were analyzed. The neutral status amino acids such as a leucine (wild-type) or a glutamine at 428 preferred heterodimerization with RXR. Furthermore, a positively charged side chain of amino acids at 428 such as an arginine or a lysine, preserved homodimer formation. Irrespective of charge, ninth heptad mutant receptors did not bind the ligand and were not able to interact with either corepressor or coactivating proteins. Limited trypsinization assays revealed no major conformational change in the ninth heptad mutant receptors. Together, these findings suggested that a leucine at 428 was a critical amino acid for both interaction with the thyroid hormone receptor associated proteins and ligand-independent and -dependent functions regardless of dimer formations.
UR - http://www.scopus.com/inward/record.url?scp=0038204773&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0038204773&partnerID=8YFLogxK
U2 - 10.1089/105072503322021089
DO - 10.1089/105072503322021089
M3 - Article
C2 - 12855009
AN - SCOPUS:0038204773
SN - 1050-7256
VL - 13
SP - 427
EP - 435
JO - Thyroid
JF - Thyroid
IS - 5
ER -