epsilon-COP is a structural component of coatomer that functions to stabilize alpha-COP

EMBO J. 1998 Feb 16;17(4):985-95. doi: 10.1093/emboj/17.4.985.

Abstract

We isolated a novel yeast alpha-COP mutant, ret1-3, in which alpha-COP is degraded after cells are shifted to a restrictive temperature. ret1-3 cells cease growth at 28 degrees C and accumulate the ER precursor of carboxypeptidase Y (p1 CPY). In a screen for high copy suppressors of these defects, we isolated the previously unidentified yeast epsilon-COP gene. epsilon-COP (Sec28p) overproduction suppresses the defects of ret1-3 cells up to 34 degrees C, through stabilizing levels of alpha-COP. Surprisingly, cells lacking epsilon-COP (sec28 Delta) grow well up to 34 degrees C and display normal trafficking of carboxypeptidase Y and KKXX-tagged proteins at a permissive temperature. epsilon-COP is thus non-essential for yeast cell growth, but sec28 Delta cells are thermosensitive. In sec28 Delta cells shifted to 37 degrees C, wild-type alpha-COP (Ret1p) levels diminish rapidly and cells accumulate p1 CPY; these defects can be suppressed by alpha-COP overproduction. Mutant coatomer from sec28 Delta cells behaves as an unusually large protein complex in gel filtration experiments. The sec28 Delta mutation displays allele-specific synthetic-lethal interactions with alpha-COP mutations: sec28 Delta ret1-3 double mutants are unviable at all temperatures, whereas sec28 Delta ret1-1 double mutants grow well up to 30 degrees C. Our results suggest that a function of epsilon-COP is to stabilize alpha-COP and the coatomer complex.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alleles
  • Amino Acid Sequence
  • Animals
  • Biological Transport / genetics
  • Carboxypeptidases / genetics
  • Cathepsin A
  • Cattle
  • Coatomer Protein
  • Genes, Fungal
  • Genes, Lethal
  • Genes, Suppressor
  • Macromolecular Substances
  • Membrane Proteins / biosynthesis
  • Membrane Proteins / chemistry*
  • Membrane Proteins / deficiency
  • Membrane Proteins / genetics
  • Membrane Proteins / isolation & purification
  • Membrane Proteins / metabolism*
  • Membrane Proteins / physiology
  • Molecular Sequence Data
  • Mutation
  • Saccharomyces cerevisiae / enzymology
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / growth & development
  • Temperature

Substances

  • Coatomer Protein
  • Macromolecular Substances
  • Membrane Proteins
  • Carboxypeptidases
  • Cathepsin A

Associated data

  • GENBANK/AF043582