TRK1 encodes a plasma membrane protein required for high-affinity potassium transport in Saccharomyces cerevisiae.

Gaber, Richard F.; Styles, Cora A.; Fink, Gerald R.

doi:10.1128/mcb.8.7.2848

Cited by 270 publications

(233 citation statements)

References 39 publications

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“…Jan and Jan [2] have proposed that the K translocating subunit TrkG from one of the two Escherichia coli Trk K uptake systems also contains two P-loop regions. Subsequently it was recognized that TrkG belongs to a broad family of K symporter proteins [3^5], consisting of HKT1 from plants [6], Trk1 and Trk2 from fungi [7,8], KtrB (NtpJ) from bacteria [3,9], and TrkH (TrkG) from prokaryotes [10,11]. Independently, the Durell-Guy group and we recognized that these proteins consist of a basic structure of four consecutive M1-P-M2 motifs ( [5,12], see Fig.…”

Section: Introductionmentioning

confidence: 99%

Change to alanine of one out of four selectivity filter glycines in KtrB causes a two orders of magnitude decrease in the affinities for both K⁺ and Na⁺ of the Na⁺ dependent K⁺ uptake system KtrAB from Vibrio alginolyticus

Tholema¹,

Bakker²,

Suzuki³

et al. 1999

FEBS Letters

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KtrAB from Vibrio alginolyticus is a recently described new type of high affinity bacterial K + uptake system. Its activity assayed in an Escherichia coli K + uptake negative mutant depended on Na + ions (K m of 40 W WM). Subunit KtrB contains four putative P-loops. The selectivity filter from each Ploop contains a conserved glycine residue. Residue Gly-290 from the third P-loop selectivity filter in KtrB was exchanged for Ala, Ser or Asp. KtrB variants Ser-290 and Asp-290 were without activity. In contrast, KtrB variant Ala-290 was still active. This variant transported K + with a two orders of magnitude decrease in apparent affinity for both K + and Na + with little effect on V max .z 1999 Federation of European Biochemical Societies.

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Section: Introductionmentioning

confidence: 99%

Change to alanine of one out of four selectivity filter glycines in KtrB causes a two orders of magnitude decrease in the affinities for both K⁺ and Na⁺ of the Na⁺ dependent K⁺ uptake system KtrAB from Vibrio alginolyticus

Tholema¹,

Bakker²,

Suzuki³

et al. 1999

FEBS Letters

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“…H KT1 cDNA from wheat roots has been identified as such by its ability to enable yeast cells with deletions of the K ϩ -uptake genes TRK1 and TRK2 to grow at low K ϩ concentrations (1)(2)(3). A detailed study of the molecular mechanism of HKT1 revealed that HKT1 mediates Na ϩ ͞K ϩ cotransport (4,5).…”

mentioning

confidence: 99%

“…Alignment studies revealed that AtHKT1 and HKT1 belong to a family of K ϩ transporter proteins present in eukaryotes and prokaryotes (6)(7)(8)(9). Other members of the family are the TRK proteins of fungi (2,3), KtrB in Vibrio aliginolyticus (10), NtpJ in Enterococcus hirae (11), TrkH in E. coli (12), and the KdpA subunit of the E. coli P-type K ϩ translocating ATPase Kdp (9,13). All of these proteins appear to have evolved from a simple, KcsA-like K ϩ channel protein of prokaryotes and eukaryotes (7-9, 14, 15).…”

mentioning

confidence: 99%

Evidence in support of a four transmembrane-pore-transmembrane topology model for the Arabidopsis thaliana Na ⁺ /K ⁺ translocating AtHKT1 protein, a member of the superfamily of K ⁺ transporters

Kato

Sakaguchi

Mori

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

127

107

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The Arabidopsis thaliana AtHKT1 protein, a Na ؉ ͞K ؉ transporter, is capable of mediating inward Na ؉ currents in Xenopus laevis oocytes and K ؉ uptake in Escherichia coli. HKT1 proteins are members of a superfamily of K ؉ transporters. These proteins have been proposed to contain eight transmembrane segments and four pore-forming regions arranged in a mode similar to that of a K ؉ channel tetramer. However, computer analysis of the AtHKT1 sequence identified eleven potential transmembrane segments. We have investigated the membrane topology of AtHKT1 with three different techniques. First, a gene fusion alkaline phosphatase study in E. coli clearly defined the topology of the N-terminal and middle region of AtHKT1, but the model for membrane folding of the C-terminal region had to be refined. Second, with a reticulocyte-lysate supplemented with dog-pancreas microsomes, we demonstrated that N-glycosylation occurs at position 429 of AtHKT1. An engineered unglycosylated protein variant, N429Q, mediated Na ؉ currents in X. laevis oocytes with the same characteristics as the wild-type protein, indicating that N-glycosylation is not essential for the functional expression and membrane targeting of AtHKT1. Five potential glycosylation sites were introduced into the N429Q. Their pattern of glycosylation supported the model based on the E. coli-alkaline phosphatase data. Third, immunocytochemical experiments with FLAG-tagged AtHKT1 in HEK293 cells revealed that the N and C termini of AtHKT1, and the regions containing residues 135-142 and 377-384, face the cytosol, whereas the region of residues 55-62 is exposed to the outside. Taken together, our results show that AtHKT1 contains eight transmembrane-spanning segments.

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“…QDR2 expression was found to confer a physiological advantage for the yeast cells under conditions leading to K ϩ -limited growth, due either to a limiting level of K ϩ in the growth medium or to the presence of quinidine. Potassium uptake in S. cerevisiae occurs essentially through the plasma membrane proteins Trk1p and Trk2p, re-sponsible for high-and moderate-affinity K ϩ transport, respectively (11,21,34). TRK1 appears to be the most important component of potassium uptake, as mutations of this gene result in a significant defect in potassium transport and the inability to grow under limiting concentrations of this cation (11,21,33,34).…”

mentioning

confidence: 99%

Saccharomyces cerevisiae Multidrug Resistance Transporter Qdr2 Is Implicated in Potassium Uptake, Providing a Physiological Advantage to Quinidine-Stressed Cells

et al. 2007

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The QDR2 gene of Saccharomyces cerevisiae encodes a putative plasma membrane drug:H ؉ antiporter that confers resistance against quinidine, barban, bleomycin, and cisplatin. This work provides experimental evidence of defective K ؉ (Rb ؉ ) uptake in the absence of QDR2. The direct involvement of Qdr2p in K ؉ uptake is reinforced by the fact that increased K ؉ (Rb ؉ ) uptake due to QDR2 expression is independent of the Trk1p/Trk2p system. QDR2 expression confers a physiological advantage for the yeast cell during the onset of K ؉ limited growth, due either to a limiting level of K ؉ in the growth medium or to the presence of quinidine. This drug decreases the K ؉ uptake rate and K ؉ accumulation in the yeast cell, especially in the ⌬qdr2 mutant. Qdr2p also helps to sustain the decrease of intracellular pH in quinidine-stressed cells in growth medium at pH 5.5 by indirectly promoting H ؉ extrusion affected by the drug. The results are consistent with the hypothesis that Qdr2p may also couple K ؉ movement with substrate export, presumably with quinidine. Other clues to the biological role of QDR2 in the yeast cell come from two additional lines of experimental evidence. First, QDR2 transcription is activated under nitrogen (NH 4 ؉ ) limitation or when the auxotrophic strain examined enters stationary phase due to leucine limitation, this regulation being dependent on general amino acid control by Gcn4p. Second, the amino acid pool is higher in ⌬qdr2 cells than in wild-type cells, indicating that QDR2 expression is, directly or indirectly, involved in amino acid homeostasis.

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TRK1 encodes a plasma membrane protein required for high-affinity potassium transport in Saccharomyces cerevisiae.

Cited by 270 publications

References 39 publications

Change to alanine of one out of four selectivity filter glycines in KtrB causes a two orders of magnitude decrease in the affinities for both K⁺ and Na⁺ of the Na⁺ dependent K⁺ uptake system KtrAB from Vibrio alginolyticus

Change to alanine of one out of four selectivity filter glycines in KtrB causes a two orders of magnitude decrease in the affinities for both K⁺ and Na⁺ of the Na⁺ dependent K⁺ uptake system KtrAB from Vibrio alginolyticus

Evidence in support of a four transmembrane-pore-transmembrane topology model for the Arabidopsis thaliana Na ⁺ /K ⁺ translocating AtHKT1 protein, a member of the superfamily of K ⁺ transporters

Saccharomyces cerevisiae Multidrug Resistance Transporter Qdr2 Is Implicated in Potassium Uptake, Providing a Physiological Advantage to Quinidine-Stressed Cells

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TRK1 encodes a plasma membrane protein required for high-affinity potassium transport in Saccharomyces cerevisiae.

Cited by 270 publications

References 39 publications

Change to alanine of one out of four selectivity filter glycines in KtrB causes a two orders of magnitude decrease in the affinities for both K+ and Na+ of the Na+ dependent K+ uptake system KtrAB from Vibrio alginolyticus

Change to alanine of one out of four selectivity filter glycines in KtrB causes a two orders of magnitude decrease in the affinities for both K+ and Na+ of the Na+ dependent K+ uptake system KtrAB from Vibrio alginolyticus

Evidence in support of a four transmembrane-pore-transmembrane topology model for the Arabidopsis thaliana Na + /K + translocating AtHKT1 protein, a member of the superfamily of K + transporters

Saccharomyces cerevisiae Multidrug Resistance Transporter Qdr2 Is Implicated in Potassium Uptake, Providing a Physiological Advantage to Quinidine-Stressed Cells

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Change to alanine of one out of four selectivity filter glycines in KtrB causes a two orders of magnitude decrease in the affinities for both K⁺ and Na⁺ of the Na⁺ dependent K⁺ uptake system KtrAB from Vibrio alginolyticus

Change to alanine of one out of four selectivity filter glycines in KtrB causes a two orders of magnitude decrease in the affinities for both K⁺ and Na⁺ of the Na⁺ dependent K⁺ uptake system KtrAB from Vibrio alginolyticus

Evidence in support of a four transmembrane-pore-transmembrane topology model for the Arabidopsis thaliana Na ⁺ /K ⁺ translocating AtHKT1 protein, a member of the superfamily of K ⁺ transporters