Potassium is an essential intracellular ion, and a sufficient intracellular concentration of it is crucial for many processes; therefore it is fundamental for cells to precisely regulate K+ uptake and efflux through the plasma membrane. The uniporter Trk1 is a key player in K+ acquisition in yeasts. The TRK1 gene is expressed at a low and stable level; thus the activity of the transporter needs to be regulated at a posttranslational level. S. cerevisiae Trk1 changes its activity and affinity for potassium ion quickly and according to both internal and external concentrations of K+, as well as the membrane potential. The molecular basis of these changes has not been elucidated, though phosphorylation is thought to play an important role. In this study, we examined the role of the second, short, and highly conserved intracellular hydrophilic loop of Trk1 (IL2), and identified two phosphorylable residues (Ser882 and Thr900) as very important for 1) the structure of the loop and consequently for the targeting of Trk1 to the plasma membrane, and 2) the upregulation of the transporter's activity reaching maximal affinity under low external K+ conditions. Moreover, we identified three residues (Thr155, Ser414, and Thr900) within the Trk1 protein as strong candidates for interaction with 14-3-3 regulatory proteins, and showed, in an in vitro experiment, that phosphorylated Thr900 of the IL2 indeed binds to both isoforms of yeast 14-3-3 proteins, Bmh1 and Bmh2.

• Klíčová slova
• 14–3–3 proteins, Phosphorylation, Potassium ion uptake, Saccharomyces cerevisiae, Trk1,
• Publikační typ
• časopisecké články MeSH

In baker's yeast (Saccharomyces cerevisiae), Trk1, a member of the superfamily of K-transporters (SKT), is the main K+ uptake system under conditions when its concentration in the environment is low. Structurally, Trk1 is made up of four domains, each similar and homologous to a K-channel α subunit. Because most K-channels are proteins containing four channel-building α subunits, Trk1 could be functional as a monomer. However, related SKT proteins TrkH and KtrB were crystallised as dimers, and for Trk1, a tetrameric arrangement has been proposed based on molecular modelling. Here, based on Bimolecular Fluorescence Complementation experiments and single-molecule fluorescence microscopy combined with molecular modelling; we provide evidence that Trk1 can exist in the yeast plasma membrane as a monomer as well as a dimer. The association of monomers to dimers is regulated by the K+ concentration.

• Klíčová slova
• K+ translocation, MD simulation, Saccharomyces cerevisiae, bimolecular fluorescence complementation, dimerisation, molecular modelling,
• MeSH
• biologický transport MeSH
• buněčná membrána metabolismus   MeSH
• draslík metabolismus   MeSH
• fungální proteiny metabolismus   MeSH
• proteiny přenášející kationty * genetika   metabolismus   MeSH
• Saccharomyces cerevisiae - proteiny * genetika   metabolismus   MeSH
• Saccharomyces cerevisiae metabolismus   MeSH
• translokace genetická MeSH
• transportní proteiny metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• draslík MeSH
• fungální proteiny MeSH
• proteiny přenášející kationty * MeSH
• Saccharomyces cerevisiae - proteiny * MeSH
• transportní proteiny MeSH
• TRK1 protein, S cerevisiae MeSH Prohlížeč