Unique Photobleaching Phenomena of the Twin-Arginine Translocase Respiratory Enzyme Chaperone DmsD

Fabrizio Rivardo, Thorin G.H. Leach, Catherine S. Chan, Tara M.L. Winstone, Carol L. Ladner, Kwabena J. Sarfo, Raymond J. Turner*
BI 156, Department of Biological Sciences, University of Calgary, 2500 University Dr NW, Calgary, Alberta, Canada T2N 1N4

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© Rivardo et al.; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the BI 156, Department of Biological Sciences, University of Calgary, 2500 University Dr NW, Calgary, Alberta, Canada T2N 1N4; Tel: 1-403-220-4308; Fax: 1-403-289-9311; E-mail: turnerr@ucalgary.ca


DmsD is a chaperone of the redox enzyme maturation protein family specifically required for biogenesis of DMSO reductase in Escherichia coli. It exists in multiple folding forms, all of which are capable of binding its known substrate, the twin-arginine leader sequence of the DmsA catalytic subunit. It is important for maturation of the reductase and targeting to the cytoplasmic membrane for translocation. Here, we demonstrate that DmsD exhibits an irreversible photobleaching phenomenon upon 280 nm excitation irradiation. The phenomenon is due to quenching of the tryptophan residues in DmsD and is dependent on its folding and conformation. We also show that a tryptophan residue involved in DmsA signal peptide binding (W87) is important for photobleaching of DmsD. Mutation of W87, or binding of the DmsA twin-arginine signal peptide to DmsD in the pocket that includes W72, W80, and W91 significantly affects the degree of photobleaching. This study highlights the advantage of a photobleaching phenomenon to study protein folding and conformation changes within a protein that was once considered unusable in fluorescence spectroscopy.

Keywords: : Photobleaching, DmsD, twin-arginine translocation, redox enzyme maturation protein.