K(+) Uptake Systems in the Yeast Hansenula Polymorpha. Transcriptional and Post-Translational Mechanisms Involved in High-Affinity K(+) Transporter Regulation

Fungal Genet Biol. 2012 Sep;49(9):755-63. doi: 10.1016/j.fgb.2012.06.008. Epub 2012 Jul 6.


We have identified the two main K(+) transporters in the yeast Hansenula polymorpha. So far this is the only yeast with these transporters amenable to molecular genetic analysis. Two ORF-encoding permeases with high similarity to Trk1 and Hak1 are present in the genome of this yeast. Deletion of either of these genes led to defective growth in low K(+). The K(+) and Rb(+) uptake rates showed high affinity of Hak1 for K(+), while the affinity estimated for Trk1 was two orders of magnitude lower. TRK1 was not transcriptionally regulated and HAK1 was strongly induced in response to very low K(+) and down-regulated by the presence of K(+). This process is clearly dependent on calcineurin. The use of a set of strains carrying mutations affecting intracellular protein trafficking revealed that in response to K(+), Hak1 is endocytosed and degraded in the vacuole, this depending on the ubiquitin ligase Rsp5. This is a first insight into the transcriptional and post-translational mechanisms regulating a high-affinity K(+) transporter (HAK-type transporter) that allows cells to respond and adapt to K(+) availability.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biological Transport
  • Calcineurin / metabolism
  • Cation Transport Proteins / genetics
  • Cation Transport Proteins / metabolism*
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism*
  • Gene Deletion
  • Gene Expression Regulation, Fungal*
  • Membrane Transport Proteins / genetics
  • Membrane Transport Proteins / metabolism*
  • Molecular Sequence Data
  • Pichia / enzymology
  • Pichia / genetics
  • Pichia / growth & development
  • Pichia / metabolism*
  • Potassium / metabolism
  • Protein Processing, Post-Translational*
  • Transcription, Genetic*


  • Cation Transport Proteins
  • Fungal Proteins
  • Membrane Transport Proteins
  • Calcineurin
  • Potassium

Associated data

  • GENBANK/HE605044
  • GENBANK/HE605045