Purification, crystallization and preliminary X-ray analysis of an unusual thioredoxin from the gastric pathogen Helicobacter pylori

Thioredoxin-2 (HP1458) from Helicobacter pylori is a member of the thioredoxin family, but possesses the unusual active-site motif CPDC (compared with CGPC in other thioredoxins). H. pylori is deficient in the glutaredoxin system, making the thioredoxin system the sole reduction system in the bacterium and critical for its ability to survive oxidative stress. The recombinant protein has been overexpressed, purified and crystallized. This is the first reported crystallization of a thioredoxin possessing this unusual active site. Single crystals have been obtained using the sitting-drop technique. Crystals diffract to 2.4 Angstrom resolution and belong to space group P4(1), with unit-cell parameters a=b=40.21, c=64.65 Angstrom. Molecular replacement using AMoRe proved unsuccessful; however, implementation of the program BEAST gave successful molecular-replacement solutions.