TY - JOUR
T1 - Structural evidence for asymmetric ligand binding to transthyretin
AU - Cianci, Michele
AU - Folli, Claudia
AU - Zonta, Francesco
AU - Florio, Paola
AU - Berni, Rodolfo
AU - Zanotti, Giuseppe
N1 - Publisher Copyright:
© 2015 International Union of Crystallography.
PY - 2015/8/1
Y1 - 2015/8/1
N2 - Human transthyretin (TTR) represents a notable example of an amyloidogenic protein, and several compounds that are able to stabilize its native state have been proposed as effective drugs in the therapy of TTR amyloidosis. The two thyroxine (T4) binding sites present in the TTR tetramer display negative binding cooperativity. Here, structures of TTR in complex with three natural polyphenols (pterostilbene, quercetin and apigenin) have been determined, in which this asymmetry manifests itself as the presence of a main binding site with clear ligand occupancy and related electron density and a second minor site with a much lower ligand occupancy. The results of an analysis of the structural differences between the two binding sites are consistent with such a binding asymmetry. The different ability of TTR ligands to saturate the two T4 binding sites of the tetrameric protein can be ascribed to the different affinity of ligands for the weaker binding site. In comparison, the high-affinity ligand tafamidis, co-crystallized under the same experimental conditions, was able to fully saturate the two T4 binding sites. This asymmetry is characterized by the presence of small but significant differences in the conformation of the cavity of the two binding sites. Molecular-dynamics simulations suggest the presence of even larger differences in solution. Competition binding assays carried out in solution revealed the presence of a preferential binding site in TTR for the polyphenols pterostilbene and quercetin that was different from the preferential binding site for T4. The TTR binding asymmetry could possibly be exploited for the therapy of TTR amyloidosis by using a cocktail of two drugs, each of which exhibits preferential binding for a distinct binding site, thus favouring saturation of the tetrameric protein and consequently its stabilization.
AB - Human transthyretin (TTR) represents a notable example of an amyloidogenic protein, and several compounds that are able to stabilize its native state have been proposed as effective drugs in the therapy of TTR amyloidosis. The two thyroxine (T4) binding sites present in the TTR tetramer display negative binding cooperativity. Here, structures of TTR in complex with three natural polyphenols (pterostilbene, quercetin and apigenin) have been determined, in which this asymmetry manifests itself as the presence of a main binding site with clear ligand occupancy and related electron density and a second minor site with a much lower ligand occupancy. The results of an analysis of the structural differences between the two binding sites are consistent with such a binding asymmetry. The different ability of TTR ligands to saturate the two T4 binding sites of the tetrameric protein can be ascribed to the different affinity of ligands for the weaker binding site. In comparison, the high-affinity ligand tafamidis, co-crystallized under the same experimental conditions, was able to fully saturate the two T4 binding sites. This asymmetry is characterized by the presence of small but significant differences in the conformation of the cavity of the two binding sites. Molecular-dynamics simulations suggest the presence of even larger differences in solution. Competition binding assays carried out in solution revealed the presence of a preferential binding site in TTR for the polyphenols pterostilbene and quercetin that was different from the preferential binding site for T4. The TTR binding asymmetry could possibly be exploited for the therapy of TTR amyloidosis by using a cocktail of two drugs, each of which exhibits preferential binding for a distinct binding site, thus favouring saturation of the tetrameric protein and consequently its stabilization.
KW - Amyloidosis
KW - Fibrillogenesis inhibitors
KW - Negative cooperativity
KW - Protein misfolding
KW - Transthyretin
KW - Transthyretin stabilizers
UR - http://www.scopus.com/inward/record.url?scp=84938837564&partnerID=8YFLogxK
U2 - 10.1107/S1399004715010585
DO - 10.1107/S1399004715010585
M3 - Article
C2 - 26249340
AN - SCOPUS:84938837564
SN - 0907-4449
VL - 71
SP - 1582
EP - 1592
JO - Acta Crystallographica Section D: Biological Crystallography
JF - Acta Crystallographica Section D: Biological Crystallography
ER -