A PEST-like sequence in the N-terminal cytoplasmic domain of Saccharomyces maltose permease is required for glucose-induced proteolysis and rapid inactivation of transport activity

Biochemistry. 2000 Apr 18;39(15):4518-26. doi: 10.1021/bi992455a.


Maltose permease is required for maltose transport into Saccharomyces cells. Glucose addition to maltose-fermenting cells causes selective delivery of this integral plasma membrane protein to the yeast vacuole via endocytosis for degradation by resident proteases. This glucose-induced degradation is independent of the proteasome but requires ubiquitin and certain ubiquitin conjugating enzymes. We used mutation analysis to identify target sequences in Mal61/HA maltose permease involved in its selective glucose-induced degradation. A nonsense mutation was introduced at codon 581, creating a truncated functional maltose permease. Additional missense mutations were introduced into the mal61/HA-581NS allele, altering potential phosphorylation and ubiquitination sites. No significant effect was seen on the rate of glucose-induced degradation of these mutant proteins. Deletion mutations were constructed, removing residues 2-30, 31-60, 61-90, and 49-78 of the N-terminal cytoplasmic domain, as well as a missense mutation of a dileucine motif. Results indicate that the proline-, glutamate-, aspartate-, serine-, and threonine-rich (PEST) sequence found in the N-terminal cytoplasmic domain, particularly residues 49-78, is required for glucose-induced degradation of Mal61/HAp and for the rapid glucose-induced inactivation of maltose transport activity. The decreased rate of glucose-induced degradation correlates with a decrease in the level of glucose-induced ubiquitination of the DeltaPEST mutant permease. In addition, newly synthesized mutant permease proteins lacking residues 49-78 or carrying an alteration in the dileucine motif, residues 69 and 70, are resistant to glucose-induced inactivation of maltose transport activity. This N-terminal PEST-like sequence is the target of both the Rgt2p-dependent and the Glc7p-Reg1p-dependent glucose signaling pathways.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Motifs
  • Amino Acid Sequence
  • Amino Acid Substitution / genetics
  • Biological Transport / drug effects
  • Carrier Proteins / chemistry*
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Fermentation
  • Fungal Proteins / chemistry*
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism*
  • Fungal Proteins / physiology
  • Glucose / pharmacology*
  • Half-Life
  • Leucine / genetics
  • Leucine / metabolism
  • Maltose / metabolism
  • Membrane Proteins / genetics
  • Membrane Proteins / physiology
  • Membrane Transport Proteins / chemistry*
  • Membrane Transport Proteins / genetics
  • Membrane Transport Proteins / metabolism*
  • Molecular Sequence Data
  • Monosaccharide Transport Proteins / genetics
  • Monosaccharide Transport Proteins / physiology
  • Protein Structure, Tertiary
  • Saccharomyces cerevisiae / drug effects
  • Saccharomyces cerevisiae / enzymology*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins*
  • Sequence Deletion / genetics
  • Signal Transduction / drug effects
  • Symporters*
  • Ubiquitins / metabolism


  • Carrier Proteins
  • Fungal Proteins
  • Membrane Proteins
  • Membrane Transport Proteins
  • Monosaccharide Transport Proteins
  • RGT2 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Symporters
  • Ubiquitins
  • maltose transport system, S cerevisiae
  • Maltose
  • maltose permease
  • Leucine
  • Glucose