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Title:The SEC9 gene is essential for exocytosis in yeast and encodes a dispensable amino terminal domain
Author(s):Champion, Kathleen M.
Doctoral Committee Chair(s):Miller, Charles G.
Department / Program:Microbiology
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Biology, Cell
Biology, Microbiology
Abstract:In the budding yeast Saccharomyces cerevisiae, the SEC9 gene product is necessary for transport of secretory vesicles from the Golgi complex to the plasma membrane. The SEC9 gene was cloned from a yeast genomic library by complementation of the temperature sensitive growth defect of sec9-4 cells. The SEC9 gene is essential for viability in yeast and maps near the centromere of Chromosome XV. The cloned SEC9 gene was sequenced and contains an open reading frame with the ability to encode a 651 residue polypeptide with a calculated molecular weight of 73,628 and a theoretical isoelectric point of 4.9. The predicted SEC9 protein (SEC9$\sb{\rm p}$) contains two short polyglutamine tracts. The most striking observation from these studies is that the putative SEC9 protein appears to be composed of two domains: an amino terminal domain that is dispensable, and a carboxy terminal domain that is predicted to form an amphiphilic helix. The carboxy terminal one-third of the putative SEC9$\sb{\rm p}$ is necessary and sufficient to complement sec9-4$\sp{ts}$ and sec9 null mutants, and displays a statistically significant similarity to SNAP-25, a synaptosomal associated protein. The sec9-4 gene bears a single basepair substitution, in the C-terminal domain, that changes a G residue to an A residue. A corresponding amino acid substitution occurs and changes residue 458 from glycine in SEC9$\sb{\rm p}$ to aspartate in sec9-4$\sb{\rm p}$. The amino acid residue that is changed in the mutant represents an identity in the alignment with SNAP-25. The data suggest that the essential functions of SEC9$\sb{\rm p}$, which acts in a late stage of secretion in yeast, are contained in a carboxy terminal domain, and this domain may demonstrate functional similarities with a protein that plays a role in the late stages of exocytosis in neurons.
Issue Date:1992
Rights Information:Copyright 1992 Champion, Kathleen M.
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9215784
OCLC Identifier:(UMI)AAI9215784

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