NMR is becoming an important tool for developing new allosteric and allo-network drugs
that bind to allosteric sites on enzymes, partially inhibiting them and causing fewer side effects than
drugs already developed that target active sites. This is based on systems thinking, in which active
enzymes and other proteins are known to be flexible and interact with each other. In other words,
proteins can exist in an ensemble of different conformations whose populations are tunable. NMR is
being used to find the pathways through which the effects of binding of an allosteric ligand propagate.
There are NMR screening assays for studying ligand binding. This includes determining the changes
in the spin lattice relaxation due to changes in the mobility of atoms involved in the binding,
measuring magnetization transfer from the protein to the ligand by saturation difference transfer NMR
(STD-NMR) and the transfer of bulk magnetization to the ligand by water-Ligand Observed via
Gradient Spectroscopy, or waterLOGSY. The chemical shifts of 1H and 15N of some of the atoms in
amino acids change when an allosteric ligand binds to a protein. So, 1H15N heteronuclear single
quantum coherence (HSQC) spectra can be used to identify key amino acids and ligand binding sites.
The NMR chemical shifts of amino acids affected by ligand binding form a network that can be
characterized. Allosteric networks can be identified by chemical shift covariance analysis (CHESCA).
This approach has been used recently to study the binding of new molecular entities (NMEs) to
potentially therapeutic drug targets.
Keywords: Allostery, CHESCA, 1H-15N HSQC, NMR, systems thinking.
Rights & PermissionsPrintExport