PDBsum entry 5ihh

Transport protein

PDB id: 5ihh

Contents

Protein chains

116 a.a.

Ligands

6B5 ×2

Metals

_NA

Waters ×258

PDB id:

5ihh

Name:

Transport protein

Title:

Crystal structure of human transthyretin in complex with luteolin-meo at 1.35 a resolution

Structure:

Transthyretin. Chain: a, b. Synonym: attr,prealbumin,tbpa. Engineered: yes

Source:

Homo sapiens. Human. Organism_taxid: 9606. Gene: ttr, palb. Expressed in: escherichia coli. Expression_system_taxid: 562

Resolution:

1.35Å R-factor: 0.141 R-free: 0.166

Authors:

A.Begum,L.Nilsson,A.Olofsson,A.E.Sauer-Eriksson

Key ref:

L.Nilsson et al. (2016). Modifications of the 7-Hydroxyl Group of the Transthyretin Ligand Luteolin Provide Mechanistic Insights into Its Binding Properties and High Plasma Specificity. PLoS One, 11, e0153112. PubMed id: 27050398

Date:

29-Feb-16 Release date: 20-Apr-16

Protein chains

P02766  (TTHY_HUMAN) -  Transthyretin from Homo sapiens

Seq: 147 a.a.

Struc: 116 a.a.

PLoS One 11:e0153112 (2016)

PubMed id: 27050398

Modifications of the 7-Hydroxyl Group of the Transthyretin Ligand Luteolin Provide Mechanistic Insights into Its Binding Properties and High Plasma Specificity.

L.Nilsson, A.Larsson, A.Begum, I.Iakovleva, M.Carlsson, K.Brännström, A.E.Sauer-Eriksson, A.Olofsson.

ABSTRACT

Amyloid formation of the plasma protein transthyretin (TTR) has been linked to familial amyloid polyneuropathy and senile systemic amyloidosis. Binding of ligands within its natural hormone binding site can stabilize the tetrameric structure and impair amyloid formation. We have recently shown that the flavonoid luteolin stabilizes TTR in human plasma with a very high selectivity. Luteolin, however, is inactivated in vivo via glucuronidation for which the preferred site is the hydroxy group at position 7 on its aromatic A-ring. We have evaluated the properties of two luteolin variants in which the 7-hydroxy group has been exchanged for a chlorine (7-Cl-Lut) or a methoxy group (7-MeO-Lut). Using an in vitro model, based on human liver microsomes, we verified that these modifications increase the persistence of the drug. Crystal structure determinations show that 7-Cl-Lut binds similarly to luteolin. The larger MeO substituent cannot be accommodated within the same space as the chlorine or hydroxy group and as a result 7-MeO-Lut binds in the opposite direction with the methoxy group in position 7 facing the solvent. Both 7-Cl-Lut and 7-MeO-Lut qualify as high-affinity binders, but in contrast to luteolin, they display a highly non-specific binding to other plasma components. The binding of the two conformations and the key-interactions to TTR are discussed in detail. Taken together, these results show a proof-of-concept that the persistence of luteolin towards enzymatic modification can be increased. We reveal two alternative high-affinity binding modes of luteolin to TTR and that modification in position 7 is restricted only to small substituents if the original orientation of luteolin should be preserved. In addition, the present work provides a general and convenient method to evaluate the efficacy of TTR-stabilizing drugs under conditions similar to an in vivo environment.