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Eukaryotic Cell doi:10.1128/EC.00151-08
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Sorting signals within the Saccharomyces cerevisiae sporulation-specific dityrosine transporter, Dtr1p, C-terminus promote Golgi-to-Prospore Membrane transport

Section of Molecular and Cellular Biology, University of California, Davis, One Shields Avenue, Davis, CA95616, USA

^* To whom correspondence should be addressed. Email: jengebrecht{at}ucdavis.edu.

	Abstract

During sporulation in Saccharomyces cerevisiae, the dityrosine transporter, Dtr1p, which is required for formation of the outermost layer of the spore wall, is specifically expressed and transported to the prospore membrane, a novel double lipid-bilayer membrane. Dtr1p consists of 572 amino acids with predicted N- and C-terminal cytoplasmic extensions and twelve trans-membrane domains. Dtr1p missing the largest internal cytoplasmic loop was trapped in the endoplasmic reticulum in both mitotically-dividing cells and cells induced to sporulate. Deletion of the carboxyl fifteen amino acids, but not the N-terminal extension of Dtr1p, resulted in a protein that failed to localize to the prospore membrane and was instead observed in cytoplasmic puncta. The puncta co-localized with a cis-Golgi marker, suggesting that Dtr1p missing the last fifteen amino acids was trapped in an early Golgi compartment. Deletion of the C-terminal ten amino acids resulted in a protein that localized to the prospore membrane with a delay and accumulated in cytoplasmic puncta that partially co-localized with a trans-Golgi marker. Both full-length and Dtr1p missing the last ten amino acids expressed in vegetative cells localized to the plasma membrane and vacuoles, while Dtr1p deleted for the carboxyl terminal fifteen amino acids was only observed at vacuoles, suggesting that transport to the prospore membrane is mediated by distinct signals from those that specify plasma membrane localization. Transfer-of-function experiments revealed that both the carboxyl trans-membrane domain and the C-terminal tail are important for Golgi-to-Prospore Membrane transport.