Exploring the structural origins of cryptic sites on proteins

Cryptic binding sites are absent or occluded in unbound proteins but present in ligand-bound structures. They can provide druggable pockets in cases where the main functional site of the protein cannot be targeted with sufficient potency or specificity. We show that unbound structures of proteins with cryptic sites have strong binding hot spots and above-average flexibility around the incipient pockets. Binding hot spots can be easily identified computationally, and protein flexibility can often be assessed by the analysis of X-ray structures of the unbound protein, including structures with low resolution. The approach presented here helps to assess the potential druggability of cryptic sites prior to running expensive screening experiments and reveals information about how cryptic sites form.