Crystallization and preliminary X-ray crystallographic data with Escherichia coli transketolase

The Escherichia coli enzyme transketolase, a dimeric protein of 2 x 70 kDa (662 amino acids) has been prepared from an overexpression system in E. coli. The purified enzyme has been crystallized from PIPES buffer pH 6.4 and ammonium sulfate. The crystals which grow as large plates diffract to greater than 1.9 A, resolution and are of the space group P2(1)2(1)2(1) with unit-cell dimensions of a = 74.6, b = 125.6 and c = 151.0 A, (Z = 8 with one transketolase dimer in the asymmetric unit). The structure has been solved by molecular replacement using the yeast transketolase enzyme structure as a search model. The enzyme is being used for large-scale biotransformations using various aldehydes and hydroxypyruvate as substrates.