Cloning, expression, purification, crystallization and preliminary X-ray diffraction analysis of propionate kinase (TdcD) from Salmonella typhimurium

Abstract

In the cell, propionate is mainly formed during β-oxidation of odd-numbered carbon-chain fatty acids, fermentation of carbohydrates and degradation of the amino acids threonine, valine, isoleucine and methionine. Recently, it has been shown that l-threonine is non-oxidatively cleaved to propionate via 2-ketobutyrate. The last step in this process, conversion of propionyl phosphate and ADP to propionate and ATP, is catalysed by propionate kinase (EC 2.7.1.-). Here, the cloning of propionate kinase (molecular weight 44 kDa) from Salmonella typhimurium with an N-terminal hexahistidine affinity tag and its overexpression in Escherichia coli are reported. Purified propionate kinase was found to cocrystallize with ADP in the hanging-drop vapour-diffusion and microbatch methods. Crystals belong to space group P3121 or P3221, with unit-cell parameters a = b = 111.47, c = 66.52 Å. A complete data set to 2.2 Å resolution has been collected using an image-plate detector system mounted on a rotating-anode X-ray generator. © 2005 International Union of Crystallography All rights reserved.