Crystallization and preliminary X-ray analysis of the glycogen synthase from Pyrococcus abyssi.

Glycogen synthase catalyzes the transfer of glucosyl residues from ADP- or UDP-glucose to the non-reducing end of a growing alpha-1,4-glucan chain. To date, no crystallographic structure of an animal/fungal glycogen synthase (family 3 of the glycosyl transferases) or a bacterial/plant glycogen/starch synthase (family 5) has been reported. This paper describes the recombinant expression, crystallization and preliminary X-ray analysis of the glycogen synthase from the hyperthermophilic archaeon Pyrococcus abyssi, the smallest enzyme of the members of families 3 and 5 of the glycosyl transferases. Crystals from this protein and from its selenomethionyl variant were grown in 100 mM sodium citrate pH 5.6 containing 20% PEG and 20% dioxane by the hanging-drop vapour-diffusion method at 293 K. The crystals, which grew as thin needles, diffracted to 3.5 A resolution and belong to space group C2, with unit-cell parameters a = 202, b = 73, c = 149 A, beta = 131 degrees. The crystallographic and biochemical data are consistent with either a dimer or a tetramer in the crystal asymmetric unit and a volume solvent content of 70 or 39%, respectively.