The Golgi-localization of yeast Emp47p depends on its di-lysine motif but is not affected by the ret1-1 mutation in alpha-COP

J Cell Biol. 1995 Nov;131(4):895-912. doi: 10.1083/jcb.131.4.895.

Abstract

The Saccharomyces cerevisiae EMP47 gene encodes a nonessential type-I transmembrane protein with sequence homology to a class of intracellular lectins defined by ERGIC-53 and VIP36. The 12-amino acid COOH-terminal cytoplasmic tail of Emp47p ends in the sequence KTKLL, which conforms with the consensus for di-lysine-based ER-localization signals. Despite the presence of this motif, Emp47p was shown to be a Golgi protein at steady-state. The di-lysine motif of Emp47p was functional when transplanted onto Ste2p, a plasma membrane protein, conferring ER localization. Nevertheless, the di-lysine motif was required for Golgi-localization of Emp47p and showed the same charge-independent, position-dependent characteristics of other di-lysine motifs. Alpha-COP has been shown to be required for ER localization of di-lysine-tagged proteins. Consistent with this finding, the Ste2p-Emp47p hybrid protein was mislocalized to the cell surface in the alpha-COP mutant, ret1-1. Surprisingly, the Golgi-localization of Emp47p was unaffected by the ret1-1 mutation. To investigate whether Emp47p undergoes retrograde transport from the Golgi to the ER like other di-lysine-tagged proteins we developed an assay to measure this step after block of forward transport in a sec12 mutant. Under these conditions retrograde transport led to a specific redistribution of Emp47p from the Golgi to the ER. This recycling occurred from a Golgi subcompartment containing alpha 1,3 mannose-modified oligosaccharides suggesting that it originated from a medial-or later Golgi compartment. Thus Emp47p cycles between the Golgi apparatus and the ER and requires a di-lysine motif for its alpha-COP-independent, steady state localization in the Golgi.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Coatomer Protein
  • Endoplasmic Reticulum / chemistry
  • Endoplasmic Reticulum / metabolism
  • Fungal Proteins / analysis*
  • Fungal Proteins / chemistry
  • Fungal Proteins / genetics
  • Golgi Apparatus / chemistry*
  • Lectins / chemistry
  • Lectins / genetics
  • Lysine / analysis
  • Mannose / metabolism
  • Mannose-Binding Lectins*
  • Mannosyltransferases / analysis
  • Membrane Proteins / analysis*
  • Membrane Proteins / chemistry
  • Membrane Proteins / genetics*
  • Molecular Sequence Data
  • Mutation / physiology
  • Saccharomyces cerevisiae / chemistry*
  • Saccharomyces cerevisiae Proteins*
  • Sequence Homology, Amino Acid
  • Subcellular Fractions
  • Vesicular Transport Proteins

Substances

  • Coatomer Protein
  • EMP47 protein, S cerevisiae
  • Fungal Proteins
  • Lectins
  • Mannose-Binding Lectins
  • Membrane Proteins
  • Saccharomyces cerevisiae Proteins
  • Vesicular Transport Proteins
  • Mannosyltransferases
  • Lysine
  • Mannose

Associated data

  • GENBANK/X87622