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Published April 1992 | Published
Journal Article Open

Alternative pathways for the sorting of soluble vacuolar proteins in yeast: a vps35 null mutant missorts and secretes only a subset of vacuolar hydrolases


vps35 mutants of Saccharomyces cerevisiae exhibit severe defects in the localization of carboxypeptidase Y, a soluble vacuolar hydrolase. We have cloned the wild-type VPS35 gene by complementation of the vacuolar protein sorting defect exhibited by the vps35-17 mutant. Sequence analysis revealed an open reading frame predicted to encode a protein of 937 amino acids that lacks any obvious hydrophobic domains. Subcellular fractionation studies indicated that 80% of Vps35p peripherally associates with a membranous particulate cell fraction. The association of Vps35p with this fraction appears to be saturable; when overproduced, the vast majority of Vps35p remains in a soluble fraction. Disruption of the VPS35 gene demonstrated that it is not essential for yeast cell growth. However, the null allele of VPS35 results in a differential defect in the sorting of vacuolar carboxypeptidase Y (CPY), proteinase A (PrA), proteinase B (PrB), and alkaline phosphatase (ALP). proCPY was quantitatively missorted and secreted by delta vps35 cells, whereas almost all of proPrA, proPrB, and proALP were retained within the cell and converted to their mature forms, indicating delivery to the vacuole. Based on these observations, we propose that alternative pathways exist for the sorting and/or delivery of proteins to the vacuole.

Additional Information

Copyright © 1992 by The American Society for Cell Biology. Under the License and Publishing Agreement, authors grant to the general public, effective two months after publication of (i.e.,. the appearance of) the edited manuscript in an online issue of MBoC, the nonexclusive right to copy, distribute, or display the manuscript subject to the terms of the Creative Commons–Noncommercial–Share Alike 3.0 Unported license (http://creativecommons.org/licenses/by-nc-sa/3.0). Submitted September 16, 1991; Accepted February 14, 1992 We thank members of the Emr lab for critically reading this manuscript and for many helpful discussions during the course of this work. We also acknowledge Tom Vida, who initially observed the selective sorting defect of a vps35 mutant. This work was supported by grants from the National Institutes of Health (GM-32703 to S.D.E. and GM-12848 to B.F.H.) and by a Swiss National Foundation Fellowship (to G.P.). S.D.E. is supported as an investigator of the Howard Hughes Medical Institute.

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