title: ERp57 binds competitively to protein disulfide isomerase and calreticulin.
abstract: In this study, we screened for protein disulfide isomerase (PDI)-binding proteins in bovine liver microsomes under strict salt concentrations, using affinity column chromatography. One main band observed using SDS-PAGE was identified as ERp57 (one of the PDI family proteins) by LC-MS/MS analysis. The K(D) value of PDI binding to ERp57 was calculated as 5.46x10(-6)M with the BIACORE system. The interactions between PDI and ERp57 occurred specifically at their a and b domains, respectively. Interestingly, low concentrations of ERp57 enhanced the chaperone activity of PDI, while high concentrations interfered with chaperone activity. On the other hand, ERp57 did not affect the isomerase activity of PDI. Additionally, following pre-incubation of ERp57 with calreticulin (CRT), decreased interactions were observed between ERp57 and PDI, and vice versa. Based on the data, we propose that once ERp57 binds to PDI or CRT, the resultant complex inhibits further interactions. Therefore, ERp57 selectively forms a protein-folding complex with PDI or CRT in ER.
authors.affiliation: Department of Bioscience and Technology, Faculty of Science and Engineering, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga 525-8577, Japan.
authors.forename: Taiji
authors.initials: T
authors.lastname: Kimura
authors.forename: Keisuke
authors.initials: K
authors.lastname: Imaishi
authors.forename: Yasunari
authors.initials: Y
authors.lastname: Hagiwara
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Horibe
authors.forename: Toshiya
authors.initials: T
authors.lastname: Hayano
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Takahashi
authors.forename: Reiko
authors.initials: R
authors.lastname: Urade
authors.forename: Koichi
authors.initials: K
authors.lastname: Kato
authors.forename: Masakazu
authors.initials: M
authors.lastname: Kikuchi
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D037282:Calreticulin / Q000378:metabolism*; D002417:Cattle; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007535:Isomerases / Q000737:chemistry / Q000378:metabolism*; D008862:Microsomes, Liver / Q000201:enzymology; D018832:Molecular Chaperones / Q000378:metabolism; D019704:Protein Disulfide-Isomerases / Q000737:chemistry / Q000378:metabolism*; D020349:Surface Plasmon Resonance
chemical_list: D037282:Calreticulin; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D007535:Isomerases; D019704:Protein Disulfide-Isomerases; C085868:PDIA3 protein, human