crystallization communications
Large-volume protein crystals are a prerequisite for neutron diffraction studies and their production represents a bottleneck in obtaining neutron structures. Many protein crystals that permit the collection of high-resolution X-ray diffraction data are inappropriate for neutron diffraction owing to a plate-type morphology that limits the crystal volume. Human fibroblast growth factor 1 crystallizes in a plate morphology that yields atomic resolution X-ray diffraction data but has insufficient volume for neutron diffraction. The thin physical dimension has been identified as corresponding to the b cell edge and the X-ray structure identified a solvent-mediated crystal contact adjacent to position Glu81 that was hypothesized to limit efficient crystal growth in this dimension. In this report, a series of mutations at this crystal contact designed to both reduce side-chain entropy and replace the solvent-mediated interface with direct side-chain contacts are reported. The results suggest that improved crystal growth is achieved upon the introduction of direct crystal contacts, while little improvement is observed with side-chain entropy-reducing mutations alone.
Keywords: protein crystallization; side-chain entropy; neutron diffraction; protein engineering; crystal growth.
Supporting information
PDB references: human fibroblast growth factor 1, E81A/K101A mutant, 3cqa, r3cqasf; G81A/E82N/K101A mutant, 3crg, r3crgsf; E81S/K101A mutant, 3crh, r3crhgsf; E81S/E82N/K101A mutant, 3cri, r3crisf