ABSTRACT
An X-ray crystal structure of Kelch-like ECH-associated protein (Keap1) co-crystallised with (1S,2R)-2-[(1S)-1-[(1,3-dioxo-2,3-dihydro-1H-isoindol-2-yl)methyl]-1,2,3,4-tetrahydroisoquinolin-2-carbonyl]cyclohexane-1-carboxylic acid (compound (S,R,S)-1 a) was obtained. This X-ray crystal structure provides breakthrough experimental evidence for the true binding mode of the hit compound (S,R,S)-1 a, as the ligand orientation was found to differ from that of the initial docking model, which was available at the start of the project. Crystallographic elucidation of this binding mode helped to focus and drive the drug design process more effectively and efficiently.
Subject(s)
Adaptor Proteins, Signal Transducing/antagonists & inhibitors , Cytoskeletal Proteins/antagonists & inhibitors , Intracellular Signaling Peptides and Proteins/antagonists & inhibitors , Isoquinolines/pharmacology , NF-E2-Related Factor 2/antagonists & inhibitors , Phthalimides/pharmacology , Animals , Crystallography, X-Ray , Dose-Response Relationship, Drug , Humans , Isoquinolines/chemical synthesis , Isoquinolines/chemistry , Kelch-Like ECH-Associated Protein 1 , Mice , Models, Molecular , Molecular Structure , Phthalimides/chemical synthesis , Phthalimides/chemistry , Structure-Activity RelationshipABSTRACT
A heteroditopic ligand H(2)-L consisting of a dihydroxybenzene (catechol)-unit linked via an amide bond to a pyridyl-unit and its methyl-protected precursor Me(2)-L were synthesized, characterized, and their photophysical properties investigated. The three accessible protonation states of the ligand, H(3)-L(+), H(2)-L, and H-L(-), showed distinct (1)H NMR, absorption and emission spectroscopic characteristics that allow pH-sensing. The spectroscopic signatures obtained act as a guide to understand the signaling mechanism of the luminescent pH and molybdate sensor [Re(bpy)(CO)(3)(H(2)-L)](+). It was found that upon deprotonation of the 2-hydroxy group of H(2)-L, a ligand-based absorption band emerges that overlaps with the Re(dπ)âbpy metal-to-ligand charge transfer (MLCT) band of the sensor, reducing the quantum yield for emission on excitation in the 370 nm region. In addition, deprotonation of the catechol-unit leads to quenching of the emission from the Re(dπ)âbpy (3)MLCT state, consistent with photoinduced electron transfer from the electron-rich, deprotonated catecholate to the Re-based luminophore. Finally, reaction of 2 equiv of [Re(bpy)(CO)(3)(H(2)-L)](+) with molybdate was shown to give the zwitterionic Mo(VI) complex [MoO(2){Re(CO)(3)(bpy)(L)}(2)], as confirmed by electrospray ionization (ESI) mass spectrometry and X-ray crystallography. The crystal structure determination revealed that two fully deprotonated sensor molecules are bound via their oxygen-donors to a cis-dioxo-MoO(2) center.
ABSTRACT
Heat shock protein 90 (Hsp90) plays a key role in stress response and protection of the cell against the effects of mutation. Herein we report the identification of an Hsp90 inhibitor identified by fragment screening using a high-concentration biochemical assay, as well as its optimisation by in silico searching coupled with a structure-based drug design (SBDD) approach.
