NMR Molecular Replacement Provides New Insights into Binding Modes to Bromodomains of BRD4 and TRIM24

Structure-based drug
discovery (SBDD) largely relies on structural
information from X-ray crystallography because traditional NMR structure
calculation methods are too time consuming to be aligned with typical
drug discovery timelines. The recently developed NMR molecular replacement
(NMR2) method dramatically reduces the
time needed to generate ligand–protein complex structures using
published structures (apo or holo) of the target protein and treating
all observed NOEs as ambiguous restraints, bypassing the laborious
process of obtaining sequence-specific resonance assignments for the
protein target. We apply this method to two therapeutic targets, the
bromodomain of TRIM24 and the second bromodomain of BRD4. We show
that the NMR2 methodology can guide SBDD
by rationalizing the observed SAR. We also demonstrate that new types
of restraints and selective methyl labeling have the potential to
dramatically reduce “time to structure” and extend the
method to targets beyond the reach of traditional NMR structure elucidation.