Abstract
The SEC13 gene was originally identified by temperature-sensitive mutations that block all protein transport from the ER to the Golgi. We have found that at a permissive temperature for growth, the sec13-1 mutation selectively blocks transport of the nitrogen-regulated amino acid permease, Gap1p, from the Golgi to the plasma membrane, but does not affect the activity of constitutive permeases such as Hip1p, Can1p, or Lyp1p. Different alleles of SEC13 exhibit different relative effects on protein transport from the ER to the Golgi, or on Gap1p activity, indicating distinct requirements for SEC13 function at two different steps in the secretory pathway. Three new genes, LST4, LST7, and LST8, were identified that are also required for amino acid permease transport from the Golgi to the cell surface. Mutations in LST4 and LST7 reduce the activity of the nitrogen-regulated permeases Gap1p and Put4p, whereas mutations in LST8 impair the activities of a broader set of amino acid permeases. The LST8 gene encodes a protein composed of WD-repeats and has a close human homologue. The LST7 gene encodes a novel protein. Together, these data indicate that SEC13, LST4, LST7, and LST8 function in the regulated delivery of Gap1p to the cell surface, perhaps as components of a post-Golgi secretory-vesicle coat.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Sequence
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Amino Acid Transport Systems
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Biological Transport
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Carbon-Oxygen Lyases / genetics
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Carrier Proteins / genetics
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Carrier Proteins / metabolism*
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Cell Membrane / metabolism
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Enzyme Activation
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Fungal Proteins / genetics
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Fungal Proteins / metabolism*
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Genes, Fungal
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Genes, Lethal
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Golgi Apparatus / metabolism
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Humans
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Intracellular Signaling Peptides and Proteins*
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Membrane Proteins / genetics
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Membrane Proteins / metabolism*
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Membrane Transport Proteins / metabolism*
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Molecular Sequence Data
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Mutagenesis
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Nuclear Pore Complex Proteins
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Saccharomyces cerevisiae / genetics
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Saccharomyces cerevisiae / metabolism*
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Saccharomyces cerevisiae Proteins / genetics
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Saccharomyces cerevisiae Proteins / metabolism*
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Sequence Homology, Amino Acid
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Vesicular Transport Proteins / genetics
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Vesicular Transport Proteins / metabolism*
Substances
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Amino Acid Transport Systems
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Carrier Proteins
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Fungal Proteins
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Intracellular Signaling Peptides and Proteins
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LST4 protein, S cerevisiae
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LST7 protein, S cerevisiae
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LST8 protein, S cerevisiae
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Membrane Proteins
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Membrane Transport Proteins
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Nuclear Pore Complex Proteins
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SEC13 protein, S cerevisiae
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Saccharomyces cerevisiae Proteins
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Vesicular Transport Proteins
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Carbon-Oxygen Lyases
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threonine synthase