Cadmium and Secondary Structure-dependent Function of a Degron in the Pca1p Cadmium Exporter

Authors

Nathan Smith, University of Nebraska-LincolnFollow
Wenzhong Wel, University of Nebraska at Lincoln
Miaoyun Zhao, University of Nebraska-LincolnFollow
Xiaojuan Quin, University of Nebraska - Lincoln
Javier Seravalli, University of Nebraska-LincolnFollow
Heejeong Kim, University of Nebraska-LincolnFollow
Jaekwon Lee, University of Nebraska-LincolnFollow

Date of this Version

2016

Citation

THE JOURNAL OF BIOLOGICAL CHEMISTRY VOL. 291, NO. 23, pp. 12420–12431, June 3, 2016

Comments

© 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Abstract

Protein turnover is a critical cellular process regulating biochemical pathways and destroying terminally misfolded or damaged proteins. Pca1p, a cadmium exporter in the yeast Saccharomyces cerevisiae, is rapidly degraded by the endoplasmic reticulum-associated degradation (ERAD) system via a cis-acting degron that exists at the 250–350 amino acid region of Pca1p and is transferable to other proteins to serve as a degradation signal. Cadmium stabilizes Pca1p in a manner dependent on the degron. This suggested that cadmium-mediated masking of the degron impedes its interaction with the molecular factors involved in the ERAD. The characteristics and mechanisms of action of the degron in Pca1p and most of those in other proteins however remain to be determined. The results presented here indicate that specific cysteine residues in a degron of Pca1p sense cadmium.Anunbiased approach selecting non-functional degrons indicated a critical role of hydrophobic amino acids in the degron for its function.Asecondary structure modeling predicted the formation of an amphipathic helix. Site-directed mutagenesis confirmed the functional significance of the hydrophobic patch. Last, hydrophobic amino acids in the degron- and cadmium-binding region affected the interaction of Pca1p with the Ssa1p molecular chaperone, which is involved in ERAD. These results reveal the mechanism of action of the degron, which might be useful for the identification and characterization of other degrons.