The yeast ZRT1 zinc transporter is regulated by zinc at both transcriptional and post-translational levels. At the post-translational level, zinc inactivates ZRT1 by inducing the removal of the protein from the plasma membrane by endocytosis. The zinc transporter is subsequently degraded in the vacuole. This regulatory system allows for the rapid shut off of zinc uptake activity in cells exposed to high zinc concentrations, thereby preventing overaccumulation of this potentially toxic metal. In this report, we examine the role of ubiquitin conjugation in this process. First, we show that ZRT1 is ubiquitinated shortly after zinc treatment and before endocytosis. Secondly, mutations in various components of the ubiquitin conjugation pathway, specifically the RSP5 ubiquitin-protein ligase and the UBC4 and UBC5 ubiquitin conjugating enzymes, inhibit both ubiquitination and endocytosis. Finally, mutation of a specific lysine residue in ZRT1 blocks both ubiquitination and endocytosis. This critical lysine, Lys-195, is located in a cytoplasmic loop region of the protein and may be the residue to which ubiquitin is attached. These results demonstrate that ubiquitin conjugation is a critical step in the signal transduction pathway that controls the rate of ZRT1 endocytosis in response to zinc.
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Research Article|
February 22 2000
Zinc-regulated ubiquitin conjugation signals endocytosis of the yeast ZRT1 zinc transporter
Raad S. GITAN;
Raad S. GITAN
1Department of Nutritional Sciences, 217 Gwynn Hall, University of Missouri-Columbia, Columbia, MO 65211, U.S.A.
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David J. EIDE
David J. EIDE
1
1To whom correspondence should be addressed (e-mail eided@;missouri.edu).
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Publisher: Portland Press Ltd
Received:
September 27 1999
Revision Received:
November 24 1999
Accepted:
December 13 1999
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 2000
2000
Biochem J (2000) 346 (2): 329–336.
Article history
Received:
September 27 1999
Revision Received:
November 24 1999
Accepted:
December 13 1999
Citation
Raad S. GITAN, David J. EIDE; Zinc-regulated ubiquitin conjugation signals endocytosis of the yeast ZRT1 zinc transporter. Biochem J 1 March 2000; 346 (2): 329–336. doi: https://doi.org/10.1042/bj3460329
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