Crystal Structures of Human Transthyretin Complexed with Glabridin

Abstract

Transthyretin (TTR) is a plasma protein implicated in human amyloid diseases. Several small molecules that bind to the thyroxine-binding site of TTR have been shown to stabilize the TTR tetramer and to inhibit amyloid fibril formation of TTR. Herein, we demonstrated that glabridin (Glab), a prenylated isoflavan isolated from Glycyrrhiza glabra L., inhibited aggregation of TTR in a thioflavin assay. The TTR-Glab complex structure revealed a novel binding mode including a CH-π interaction with A108 and a hydrogen bond with K15. A structural comparison with the wild type-apo structure revealed that the CH-π interaction with A108 was strengthened by the induced-fit conformational change upon Glab binding. Furthermore, the binding of Glab induced a rotation of the T119 side chain, and the inclusion of a water molecule, leading to stabilization of the dimer-dimer interface. These results demonstrate that Glab is a novel inhibitor of TTR fibrillization and suggest the molecular mechanism by which Glab binding stabilizes the tetramer.

Glabridin, an isoflavan from licorice root, upregulates paraoxonase 2 expression under hyperglycemia and protects it from oxidation

“…The ΔG value calculated for the PON2–glabridin interaction in this study indicates that hydrophobic forces play a major role in this binding . According to recent investigations, in interactions of glabridin with proteins, the A and C hydrophobic rings of glabridin bind to the hydrophobic site of the protein, while ring B of glabridin is located in the hydrophilic site of the protein . Glabridin possesses a highly hydrophobic subunit fused with ring A, which may explain its strong binding affinity to PON2.…”

“…Glabridin reached a maximum concentration (87 nmol/L) 1 h after administration, which decreased gradually over 24 h. These findings imply that like other flavonoids, glabridin's beneficial effect might be exerted by a mechanism that is not necessarily related to its antioxidant property. Accumulating evidence indicates that glabridin, like other flavonoids, interacts directly with proteins and modulates their activities .…”

“…Trp‐fluorescence quenching has often been applied to study the binding of small organic molecules to proteins and has recently been employed to study the binding of glabridin to proteins . We applied this procedure to compare the binding affinities of glabridin to the proteins PON2, iNOS, and Mn‐SOD, which were recently discovered to be regulated by glabridin.…”

Stability and crystal structures of His88 mutant human transthyretins

“…DSSP analysis indicated that the H88 mutants adopted secondary structures similar to that of the WT (Table S2) . The quaternary structures of the H88 mutants were superimposed on that of the WT (PDB ID: http://www.rcsb.org/pdb/search/structidSearch.do?structureId=4N85) , resulting in RMSD values higher than that for the V30M mutant (PDB ID: http://www.rcsb.org/pdb/search/structidSearch.do?structureId=4PWE) (Table ) , which is the most prevalent cause of FAP. These results implied that the quaternary structures were more influenced by the mutations at the 88 position than by those at the 30 position.…”

Inhibition of the Amyloidogenesis of Transthyretin by Natural Products and Synthetic Compounds

“…The TTR amyloid fibril formation assay was performed according to the previous study. 24) Briefly, V30M-TTR was incubated in the presence of the compounds at pH 4.5 for 4 d, and then the amyloid fibrils were quantified using thioflavin-T by fluorometry (excitation: 440 nm; emission: 484 nm).…”