Functionalization of the BCL6 BTB domain into a non-covalent crystallization chaperone

The production of diffraction-quality protein crystals is challenging and often requires bespoke, time-consuming and expensive strategies. We have developed a system in which the BCL6 BTB domain acts as crystallization chaperone and promiscuous assembly block that may form the basis for Affinity Capture Crystallography. The protein of interest is expressed with a C-terminal tag that interacts with the BTB domain, and co-crystallization leads to its incorporation within a BTB-domain lattice. We used this strategy to solve the structure of the SH3 domain of human nebulin, a structure previously solved by NMR, to 1.56Å resolution. This approach is simple and effective, requiring only routine protein complexation and crystallization screening, and should be applicable to a range of proteins.