A cryoprotectant induces conformational change in glyceraldehyde-3-phosphate dehydrogenase

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a glycolytic enzyme, catalyses the conversion of D-glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate. While mammalian and yeast GAPDHs are multifunctional proteins that have additional functions beyond those involved in glycolysis, including reactions related to nuclear RNA transport, DNA replication/repair, membrane fusion and cellular apoptosis, Escherichia coli GAPDH (ecGAPDH) has only been reported to function in glycolysis. The S-loop of GAPDH is required for interaction with its cofactor and with other proteins. In this study, the three-dimensional crystal structure of GAPDH treated with trehalose is reported at 2.0 Å resolution. Trehalose was used as a cryoprotectant for the GAPDH crystals. The structure of trehalose-bound ecGAPDH was compared with the structures of both NAD⁺-free and NAD⁺-bound ecGAPDH. At the S-loop, the bound trehalose in the GAPDH structure induces a 2.4° rotation compared with the NAD⁺-free ecGAPDH structure and a 3.1° rotation compared with the NAD⁺-bound ecGAPDH structure.