Dataset Information

TRK1 and TRK2 encode structurally related K+ transporters in Saccharomyces cerevisiae.

ABSTRACT: We describe the cloning and molecular analysis of TRK2, the gene likely to encode the low-affinity K+ transporter in Saccharomyces cerevisiae. TRK2 encodes a protein of 889 amino acids containing 12 putative membrane-spanning domains (M1 through M12), with a large hydrophilic region between M3 and M4. These structural features closely resemble those contained in TRK1, the high-affinity K+ transporter. TRK2 shares 55% amino acid sequence identity with TRK1. The putative membrane-spanning domains of TRK1 and TRK2 share the highest sequence conservation, while the large hydrophilic regions between M3 and M4 exhibit the greatest divergence. The different affinities of TRK1 trk2 delta cells and trk1 delta TRK2 cells for K+ underscore the functional independence of the high- and low-affinity transporters. TRK2 is nonessential in TRK1 or trk1 delta haploid cells. The viability of cells containing null mutations in both TRK1 and TRK2 reveals the existence of an additional, functionally independent potassium transporter(s). Cells deleted for both TRK1 and TRK2 are hypersensitive to low pH; they are severely limited in their ability to take up K+, particularly when faced with a large inward-facing H+ gradient, indicating that the K+ transporter(s) that remains in trk1 delta trk2 delta cells functions differently than those of the TRK class.

SUBMITTER: Ko CH

PROVIDER: S-EPMC361257 | biostudies-other | 1991 Aug

REPOSITORIES: biostudies-other

ACCESS DATA

Publications

TRK1 and TRK2 encode structurally related K+ transporters in Saccharomyces cerevisiae.

Ko C H CH Gaber R F RF

Molecular and cellular biology 19910801 8

We describe the cloning and molecular analysis of TRK2, the gene likely to encode the low-affinity K+ transporter in Saccharomyces cerevisiae. TRK2 encodes a protein of 889 amino acids containing 12 putative membrane-spanning domains (M1 through M12), with a large hydrophilic region between M3 and M4. These structural features closely resemble those contained in TRK1, the high-affinity K+ transporter. TRK2 shares 55% amino acid sequence identity with TRK1. The putative membrane-spanning domains ...[more]

PMID: 2072919

Similar Datasets

Project description:In Saccharomyces cerevisiae, TRK1 and TRK2 are required for high- and low-affinity K+ transport. Among suppressors of the K+ transport defect in trk1 delta trk2 delta cells, we have identified members of the sugar transporter gene superfamily. One suppressor encodes the previously identified glucose transporter HXT1, and another encodes a new member of this family, HXT3. The inferred amino acid sequence of HXT3 is 87% identical to that of HXT1, 64% identical to that of HXT2, and 32% identical to that of SNF3. Like HXT1 and HXT2, overexpression of HXT3 in snf3 delta cells confers growth on low-glucose or raffinose media. The function of another new member of the HXT superfamily, HXT4 (previously identified by its ability to suppress the snf3 delta phenotype; L. Bisson, personal communication), was revealed in experiments that deleted all possible combinations of the five members of the glucose transporter gene family. Neither SNF3, HXT1, HXT2, HXT3, nor HXT4 is essential for viability. snf3 delta hxt1 delta hxt2 delta hxt3 delta hxt4 delta cells are unable to grow on media containing high concentrations of glucose (5%) but can grow on low-glucose (0.5%) media, revealing the presence of a sixth transporter that is itself glucose repressible. This transporter may be negatively regulated by SNF3 since expression of SNF3 abolishes growth of hxt1 delta hxt2 delta hxt3 delta hxt4 delta cells on low-glucose medium. HXT1, HXT2, HXT3, and HXT4 can function independently: expression of any one of these genes is sufficient to confer growth on medium containing at least 1% glucose. A synergistic relationship between SNF3 and each of the HXT genes is suggested by the observation that SNF2 hxt1 delta hxt2 delta hxt3 delta hxt4 delta cells and snf3 delta HXT1 HXT2 HXT3 HXT4 cells are unable to grow on raffinose (low fructose) yet SNF3 in combination with any single HXT gene is sufficient for growth on raffinose. HXT1 and HXT3 are differentially regulated. HXT1::lacZ is maximally expressed during exponential growth whereas HXT3::lacZ is maximally expressed after entry into stationary phase.

Project description:When expressed in Saccharomyces cerevisiae using either of two constitutive yeast promoters (PGK1prom and CCW12prom), the transporters CDT-1 and CDT-2 from the filamentous fungus Neurospora crassa are able to catalyze, respectively, active transport and facilitated diffusion of cellobiose (and, for CDT-2, also xylan and its derivatives). In S. cerevisiae, endogenous permeases are removed from the plasma membrane by clathrin-mediated endocytosis and are marked for internalization through ubiquitinylation catalyzed by Rsp5, a HECT class ubiquitin:protein ligase (E3). Recruitment of Rsp5 to specific targets is mediated by a 14-member family of endocytic adaptor proteins, termed α-arrestins. Here we demonstrate that CDT-1 and CDT-2 are subject to α-arrestin-mediated endocytosis, that four α-arrestins (Rod1, Rog3, Aly1, and Aly2) are primarily responsible for this internalization, that the presence of the transport substrate promotes transporter endocytosis, and that, at least for CDT-2, residues located in its C-terminal cytosolic domain are necessary for its efficient endocytosis. Both α-arrestin-deficient cells expressing CDT-2 and otherwise wild-type cells expressing CDT-2 mutants unresponsive to α-arrestin-driven internalization exhibit an increased level of plasma membrane-localized transporter compared to that of wild-type cells, and they grow, utilize the transport substrate, and generate ethanol anaerobically better than control cells.ImportanceEthanolic fermentation of the breakdown products of plant biomass by budding yeast Saccharomyces cerevisiae remains an attractive biofuel source. To achieve this end, genes for heterologous sugar transporters and the requisite enzyme(s) for subsequent metabolism have been successfully expressed in this yeast. For one of the heterologous transporters examined in this study, we found that the amount of this protein residing in the plasma membrane was the rate-limiting factor for utilization of the cognate carbon source (cellobiose) and its conversion to ethanol.

Dataset Information

TRK1 and TRK2 encode structurally related K+ transporters in Saccharomyces cerevisiae.

Publications

TRK1 and TRK2 encode structurally related K+ transporters in Saccharomyces cerevisiae.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets