Crystallization and preliminary diffraction studies of TraF, a component of the Escherichia coli type IV secretory system

TraF, a component of the Escherichia coli type IV secretory system, has been crystallized and preliminary X‐ray diffraction data have been collected. TraF is a 26 kDa protein encoded by the E. coli F plasmid and is required for conjugative plasmid transfer and the formation of sex pili. The N‐terminal domain of TraF has no recognizable sequence features, whereas the C‐terminal domain is believed to adopt a thioredoxin fold. However, since the active‐site cysteines of thioredoxin‐like proteins are not conserved in TraF, its biochemical role remains unclear. TraF crystallizes in space group C2, with unit‐cell parameters a = 119.87, b = 34.36, c = 46.21 Å, β = 90.40°, and crystals diffract to 2.3 Å resolution.