Darby N J, Penka E, Vincentelli R
European Molecular Biology Laboratory, Heidelberg, Germany.
J Mol Biol. 1998 Feb 13;276(1):239-47. doi: 10.1006/jmbi.1997.1504.
Protein disulfide isomerase (PDI) catalyzes protein folding linked to disulfide bond formation in secreted proteins. It consists of four major domains, denoted a, b, b' and a'. The a and a' domains each contain an active site motif, -CGHC-, which is directly involved in thiol-disulfide exchange reactions during catalysis. The roles of the b and b' domains and the functional necessity for the multi-domain structure of PDI are unknown. We now demonstrate that full catalytic activity requires the involvement of multiple PDI domains and that the b' domain has a particularly important role in catalysis. Reconstruction of the PDI molecule from the isolated a and a' domains results in a progressive increase in catalytic efficiency as further domains are added. These effects are especially significant in the catalysis of disulfide bond rearrangements in folded substrates, for which all the domains of the protein are required for maximum catalytic efficiency. It is likely that all of the domains of PDI participate in substrate binding interactions and that PDI has evolved its multidomain structure as an adaptation that allows it to catalyze transformations involving difficult conformational changes.
蛋白质二硫键异构酶（PDI）催化与分泌蛋白中二硫键形成相关的蛋白质折叠。它由四个主要结构域组成，分别称为a、b、b'和a'。a和a'结构域各自包含一个活性位点基序-CGHC-，在催化过程中直接参与硫醇-二硫键交换反应。b和b'结构域的作用以及PDI多结构域结构的功能必要性尚不清楚。我们现在证明，完整的催化活性需要多个PDI结构域的参与，并且b'结构域在催化中具有特别重要的作用。从分离的a和a'结构域重建PDI分子时，随着更多结构域的添加，催化效率会逐渐提高。这些效应在折叠底物中二硫键重排的催化中尤为显著，对于这种情况，蛋白质的所有结构域对于最大催化效率都是必需的。PDI的所有结构域可能都参与底物结合相互作用，并且PDI进化出其多结构域结构是一种适应性变化，使其能够催化涉及困难构象变化的转化。
