Identification and characterization of GmPDIL7, a soybean ER membrane-bound protein disulfide isomerase family protein.
Most proteins synthesized in the endoplasmic reticulum (ER) possess intramolecular and intermolecular disulfide bonds, which play an important role in the conformational stability and function of proteins. Hence, eukaryotic cells contain protein disulfide bond formation pathways such as the protein disulfide isomerase (PDI)-ER oxidoreductin 1 (Ero1) system in the ER lumen. In this study, we identified soybean PDIL7 (GmPDIL7), a novel soybean ER membrane-bound PDI family protein, and determined its enzymatic properties. GmPDIL7 has a putative N-terminal signal sequence, a thioredoxin domain with an active center motif (CGHC), and a putative C-terminal transmembrane region. Likewise, we demonstrated that GmPDIL7 is ubiquitously expressed in soybean tissues and is localized in the ER membrane. Furthermore, GmPDIL7 associated with other soybean PDI family proteins in vivo and GmPDIL7 mRNA was slightly upregulated under ER stress. The redox potential of recombinant GmPDIL7 expressed in Escherichia coli was -187 mV, indicating that GmPDIL7 could oxidize unfolded proteins. GmPDIL7 exhibited a dithiol oxidase activity level that was similar to other soybean PDI family proteins. However, the oxidative refolding activity of GmPDIL7 was lower than other soybean PDI family proteins. GmPDIL7 was well oxidized by GmERO1. Taken together, our results indicated that GmPDIL7 primarily plays a role as a supplier of disulfide bonds in nascent proteins for oxidative folding on the ER membrane.


DATABASE
The nucleotide sequence data for the GmPDIL7 cDNA are available in the DNA Data Bank of Japan (DDBJ) databases under the accession numbers LC158001.


ENZYME
Protein disulfide isomerase: EC 5.3.4.1.
['Okuda|Aya|A|', 'Matsusaki|Motonori|M|', 'Masuda|Taro|T|', 'Urade|Reiko|R|']
D000595:Amino Acid Sequence D003001:Cloning, Molecular D004721:Endoplasmic Reticulum D004926:Escherichia coli D015870:Gene Expression D010084:Oxidation-Reduction D010940:Plant Proteins D011485:Protein Binding D019704:Protein Disulfide-Isomerases D000072417:Protein Domains D021382:Protein Sorting Signals D012333:RNA, Messenger D011994:Recombinant Proteins D016415:Sequence Alignment D013025:Soybeans
soybean protein disulfide isomerase endoplasmic reticulum ERO1 protein folding