Abstract: The wheat protein disulfide isomerase (wPDI) contains four thioredoxin domains a-b-b'-a' and a C-ter- minal tail c.In order to investigate the effect of each domain of wPDI on its properties,eight truncated proteins of wPDI containing different domain combinations were constructed by subcloning.The target proteins were prepared after expression and purification,and then their enzymatic properties and products of protein electrophoresis were determined and analyzed.The results indicate that eight truncated proteins of wPDI are expressed in E.coli BL21,and that,after the metal chelate affinity chromatography and the size exclusion chromatography,the truncated pro- teins of wPDI of high purity are obtained.The results from activities assay indicate that all domains of wPDI contrib- ute to its disulfide bond oxidoreductase activity and molecular chaperone activity,and that,the truncation of tail c has no effect on its isomerase activity but retains the critical amino acid binding site for the molecular chaperone ac- tivity.Moreover,the electrophoretic analysis of the truanted proteins A and A' demonstrates that the active-site cys- teines in domain a are primarily in an oxidized state while those of domain a' are primarily in a reduced state.Therefore,these results lay a foundation for deeply understanding the function and property of wPDI.

Key words: wheat, protein disulfide isomerase, domain, truncated protein, active-site