Abstact

As a first step in dissecting the structure of human protein disulfide isomerase (PDI), the structure of a fragment corresponding to the first 120 residues of its sequence has been determined using heteronuclear multidimensional NMR techniques. As expected from its primary structure homology, the fragment has the thioredoxin fold. Similarities and differences in their structures help to explain why thioredoxins are reductants, whereas PDI is an oxidant of protein thiol groups. The results confirm that PDI has a modular, multidomain structure, which will facilitate its structural and functional characterization.