ИСТИНА

Potassium ions are known to play crucial role in cell physiology, especially in membrane processes. S. cerevisiae demonstrating ability to grow in a wide range of K+ concentrations is used as a model organism for ion fluxes studies. The main potassium translocation system in S. cerevisiae is encoded by Trk1 high-affinity K+-translocation protein, allowing to survive on low (μM) potassium concentrations. The structure of Trk1 is thought to consist of 2 (or according to other data 4) identical protomers, each of them containing four domains (A-D) on one peptide chain. The domains are homologous to K-channel subunits with a long hydrophilic loop (LHL) between A and B domains. But still, these models provide only medium resolution structures as they are based on a template with low sequence identity. Bimolecular Fluorescence Complementation (BiFC) was applied to study possible interactions between Trk1 parts. The method is based on fluorescence reconstitution of two non-fluorescent parts of a split fluorescent protein when they are brought in close proximity. It can be used to search for interactions between (parts of) proteins when the fragments of the fluorescent protein are fused to proteins (domains) of interest3. We aimed at examining interactions between previously not studied combination – C- and ABD-parts of Trk1.