Three Candida albicans potassium uptake systems differ in their ability to provide Saccharomyces cerevisiae trk1trk2 mutants with necessary potassium

FEMS Yeast Res. 2016 Jun;16(4):fow039. doi: 10.1093/femsyr/fow039. Epub 2016 Apr 21.

Abstract

Yeasts usually have one or two high-affinity potassium transporters. Two complete and one interrupted gene encoding three types of putative potassium uptake system exist in Candida albicans SC5314. As high intracellular potassium is essential for many yeast cell functions, the existence of three transporters with differing transport mechanisms (Trk uniporter, Hak cation-proton symporter, Acu ATPase) may help pathogenic C. albicans cells to acquire the necessary potassium in various organs and tissues of the host. When expressed in Saccharomyces cerevisiae lacking their own potassium uptake systems, all three putative transporters were able to provide cells with the ability to grow with low amounts of potassium over a broad range of external pH. Only CaTrk1 was properly recognized and secreted to the plasma membrane. Nevertheless, even the small number of CaHak1 and mainly CaAcu1 molecules which reached the plasma membrane resulted in an improved growth of cells in low potassium concentrations, suggesting a high affinity and capacity of the transporters. A single-point mutation restored the complete CaACU1 gene, and the resulting protein not only provided cells with the necessary potassium but also improved their tolerance to toxic lithium. In contrast to its known homologues, CaAcu1 did not seem to transport sodium.

Keywords: Acu1 ATPase; Candida; Hak1 transporter; Trk1 transporter; cation homeostasis; potassium uptake.

MeSH terms

  • Candida albicans / genetics
  • Candida albicans / metabolism*
  • Cation Transport Proteins / deficiency*
  • Culture Media / chemistry
  • Genetic Complementation Test
  • Hydrogen-Ion Concentration
  • Membrane Transport Proteins / genetics
  • Membrane Transport Proteins / metabolism*
  • Potassium / metabolism*
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae / growth & development
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins

Substances

  • Cation Transport Proteins
  • Culture Media
  • Membrane Transport Proteins
  • Recombinant Proteins
  • Saccharomyces cerevisiae Proteins
  • TRK2 protein, S cerevisiae
  • Trk1 protein, Candida albicans
  • TRK1 protein, S cerevisiae
  • Potassium