Crystallization and preliminary X-ray data for the A-isozyme of O-acetylserine sulfhydrylase from Salmonella typhimurium.
The A-isozyme of O-acetylserine sulfhydrylase, a pyridoxal phosphate-dependent enzyme isolated from Salmonella typhimurium catalyzes the synthesis of L-cysteine from O-acetyl-L-serine and sulfide. The pyridoxal form of the enzyme has been crystallized in two different forms. One form is in the orthorhombic space group P2(1)2(1)2(1) with cell constants a = 144.4 A, b = 96.9 A and c = 54.3 A and contains two monomers each of molecular weight 34,000 per asymmetric unit. The second form is in a hexagonal space group with unit cell dimensions a = b = 115 A, and c = 348 A and contains two 68,000 dimers per asymmetric unit. Complete native enzyme data sets have been collected for both crystal forms using an R-Axis II detector. A search for suitable heavy-atom derivatives is underway. Although both crystal forms diffract X-rays to better than 2.5 A, the orthorhombic form is more suited to a detailed structural analysis due to the extended lifetime in the X-ray beam and the relative size of the unit cell.
Department of Biochemistry and Molecular Biology, Texas College of Osteopathic Medicine, Fort Worth 76107.
G S
GS
Rao
J
J
Mottonen
E J
EJ
Goldsmith
P F
PF
Cook
D003460:Crystallization; D003547:Cysteine Synthase / Q000737:chemistry*; D007527:Isoenzymes / Q000737:chemistry; D012486:Salmonella typhimurium / Q000201:enzymology*; D014961:X-Ray Diffraction
D007527:Isoenzymes; D003547:Cysteine Synthase