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 fusi on protein with glutathione-S-transferase and purified after thrombin cleav age. Two forms of ab crystal were obtained with polyethylene glycol as prec ipitant and different additives at pH 7.5. The space group of form I is P4( 1)2(1)2 or P4(3)2(1)2, with unit-cell dimensions a = 81.5, c = 259.7 Angstr om. The space group of form II is P4(1)22 or P4(3)22, with unit-cell dimens ions a = 82.7, c = 86.5 Angstrom.