Yeast Trk1 Potassium Transporter Gradually Changes Its Affinity in Response to Both External and Internal Signals

0557979 - FGÚ 2023 RIV CH eng J - Journal Article
Masaryk, Jakub - Sychrová, Hana
Yeast Trk1 Potassium Transporter Gradually Changes Its Affinity in Response to Both External and Internal Signals.
Journal of Fungi. Roč. 8, č. 5 (2022), č. článku 432. E-ISSN 2309-608X
R&D Projects: GA ČR(CZ) GA20-04420S
Institutional support: RVO:67985823
Keywords : cation homeostasis * Saccharomyces cerevisiae * potassium uptake * membrane potential
OECD category: Microbiology
Impact factor: 4.7, year: 2022
Method of publishing: Open access
https://www.mdpi.com/2309-608X/8/5/432

Yeasts need a high intracellular concentration of potassium to grow. The main K+ uptake system in Saccharomyces cerevisiae is the Trk1 transporter, a complex protein with four MPM helical membrane motifs. Trk1 has been shown to exist in low- or high-affinity modes, which reflect the availability of potassium in the environment. However, when and how the affinity changes, and whether the potassium availability is the only signal for the affinity switch, remains unknown. Here, we characterize the Trk1 kinetic parameters under various conditions and find that Trk1's K-T and V-max change gradually. This gliding adjustment is rapid and precisely reflects the changes in the intracellular potassium content and membrane potential. A detailed characterization of the specific mutations in the P-helices of the MPM segments reveals that the presence of proline in the P-helix of the second and third MPM domain (F820P and L949P) does not affect the function of Trk1 in general, but rather specifically prevents the transporter's transition to a high-affinity state. The analogous mutations in the two remaining MPM domains (L81P and L1115P) result in a mislocalized and inactive protein, highlighting the importance of the first and fourth P-helices in proper Trk1 folding and activity at the plasma membrane.
Permanent Link: http://hdl.handle.net/11104/0331853