Title

Protein-disulfide Isomerase Displaces the Cholera Toxin A1 Subunit from the Holotoxin without Unfolding the A1 Subunit

Authors

Authors

M. Taylor; T. Banerjee; S. Ray; S. A. Tatulian;K. Teter

Comments

Authors: contact us about adding a copy of your work at STARS@ucf.edu

Abbreviated Journal Title

J. Biol. Chem.

Keywords

RETICULUM-ASSOCIATED DEGRADATION; TRANSFORM INFRARED-SPECTROSCOPY; CHO-CELLS RESISTANT; ENDOPLASMIC-RETICULUM; RETRO-TRANSLOCATION; THERMAL-STABILITY; FTIR SPECTROSCOPY; MAMMALIAN-CELLS; RICIN; CYTOSOL; Biochemistry & Molecular Biology

Abstract

Protein-disulfide isomerase (PDI) has been proposed to exhibit an "unfoldase" activity against the catalytic A1 subunit of cholera toxin (CT). Unfolding of the CTA1 subunit is thought to displace it from the CT holotoxin and to prepare it for translocation to the cytosol. To date, the unfoldase activity of PDI has not been demonstrated for any substrate other than CTA1. An alternative explanation for the putative unfoldase activity of PDI has been suggested by recent structural studies demonstrating that CTA1 will unfold spontaneously upon its separation from the holotoxin at physiological temperature. Thus, PDI may simply dislodge CTA1 from the CT holotoxin without unfolding the CTA1 subunit. To evaluate the role of PDI in CT disassembly and CTA1 unfolding, we utilized a real-time assay to monitor the PDI-mediated separation of CTA1 from the CT holotoxin and directly examined the impact of PDI binding on CTA1 structure by isotope-edited Fourier transform infrared spectroscopy. Our collective data demonstrate that PDI is required for disassembly of the CT holotoxin but does not unfold the CTA1 subunit, thus uncovering a new mechanism for CTA1 dissociation from its holotoxin.

Journal Title

Journal of Biological Chemistry

Volume

286

Issue/Number

25

Publication Date

1-1-2011

Document Type

Article

Language

English

First Page

22090

Last Page

22100

WOS Identifier

WOS:000291719900015

ISSN

0021-9258

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