W0167

Crystal Structure of Glucose-6-phosphate Isomerase from Baker's Yeast. J. K. Mohana Rao and Alexander Wlodawer, Macromolecular Structure Laboratory, ABL-BRP, NCI-FCRDC, Frederick, MD 21702 USA

Glucose-6-phosphate isomerase (GPI), also known as neuroleukin, is an important enzyme in the glycolytic pathway. GPI reversibly catalyzes glucose-6-phosphate to fructose-6-phosphate. GPI is a dimer with each monomer having 553 amino acid residues. GPI from baker's yeast crystallizes in a tetragonal unit cell of dimensions a = 136.2, c = 137.5 Å in the space group P4₂22. The crystals presently diffract to a resolution of 2.2 Å. There are two monomers in the asymmetric part of the unit cell. Interestingly enough, these two monomers are not related by a two-fold symmetry, but by a non-crystallographic translational symmetry (approximately at 1/2, 1/2, 1/3) as evidenced by the native Patterson synthesis. Efforts are being made to solve the structure using the C-alpha model of the pig GPI enzyme [Shaw and Muirhead: J. Mol. Biol. (1977) 109, 475-485] as well as heavy-atom methods. The results will be presented.

Research sponsored in part by the National Cancer Institute, DHHS, under contract with ABL.