Purification, crystallization and preliminary crystallographic studies on the N-terminal fragment of human protein disulfide isomerase

A fragment of human protein disulfide isomerase composed of the thioredoxin-like a and b domains (ab) has been expressed in Escherichia coli as a fusion protein with glutathione-S-transferase and purified after thrombin cleavage. Two forms of ab crystal were obtained with polyethylene glycol as precipitant and different additives at pH 7.5. The space group of form I is P4₁2₁2 or P4₃2₁2, with unit-cell dimensions a = 81.5, c = 259.7 Å. The space group of form II is P4₁22 or P4₃22, with unit-cell dimensions a = 82.7, c = 86.5 Å.