Improvement of crystal growth of human acidic FGF by protein engineering for neutron crystallography

Adachi, Motoyasu; Honjo, Eijiro; Tamada, Taro; Blaber, M.*; Kuroki, Ryota

Human acidic fibroblast growth factor (haFGF) is a powerful mitogen and angiogenic factor. Our objective is to reveal structure function relationships of haFGF by protein neutron crystallography. For the determination of neutron crystal structures, large crystal in size is required. Since haFGF forms thin crystals, we tried improvement of crystal growth by changing amino acids at molecular interface. The analysis using X-ray crystal structure showed that the residue of Glu81 is located near Glu81 generated by crystallographic symmetry. Therefore, Glu81 was replaced with Ala, Val, Leu, Ser and Thr residue. The mutants of E81S and E81T provided larger crystal in size than that of WT. The X-ray structures of E81S and E81T showed that a molecule of formic acid bridges between the two Glu81 residues by hydrogen bonding.