A refined atomic scale model of the Saccharomyces cerevisiae K+-translocation protein Trk1p combined with experimental evidence confirms the role of selectivity filter glycines and other key residues
Language English Country Netherlands Media print-electronic
Document type Journal Article, Research Support, Non-U.S. Gov't
PubMed
25687974
DOI
10.1016/j.bbamem.2015.02.007
PII: S0005-2736(15)00047-4
Knihovny.cz E-resources
- Keywords
- Eukaryotic Trk, Homology modeling, K(+)-translocation, Molecular dynamics, Saccharomyces cerevisiae, Selectivity filter,
- MeSH
- Cell Membrane chemistry metabolism MeSH
- Potassium metabolism MeSH
- Ion Channel Gating * MeSH
- Glycine MeSH
- Kinetics MeSH
- Protein Conformation MeSH
- Conserved Sequence MeSH
- Aspartic Acid MeSH
- Lysine MeSH
- Molecular Sequence Data MeSH
- Mutation MeSH
- Mutagenesis, Site-Directed MeSH
- Cell Membrane Permeability MeSH
- Cation Transport Proteins chemistry genetics metabolism MeSH
- Saccharomyces cerevisiae Proteins chemistry genetics metabolism MeSH
- Protein Folding MeSH
- Amino Acid Sequence MeSH
- Molecular Dynamics Simulation MeSH
- Protein Stability MeSH
- Computational Biology MeSH
- Structure-Activity Relationship MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Names of Substances
- Potassium MeSH
- Glycine MeSH
- Aspartic Acid MeSH
- Lysine MeSH
- Cation Transport Proteins MeSH
- Saccharomyces cerevisiae Proteins MeSH
- TRK1 protein, S cerevisiae MeSH Browser
Potassium ion (K+) uptake in yeast is mediated mainly by the Trk1/2 proteins that enable cells to survive on external K+ concentration as low as a few μM. Fungal Trks are related to prokaryotic TRK and Ktr and plant HKT K+ transport systems. Overall sequence similarity is very low, thus requiring experimental verification of homology models. Here a refined structural model of the Saccharomyces cerevisiae Trk1 is presented that was obtained by combining homology modeling, molecular dynamics simulation and experimental verification through functional analysis of mutants. Structural models and experimental results showed that glycines within the selectivity filter, conserved among the K-channel/transporter family, are not only important for protein function, but are also required for correct folding/membrane targeting. A conserved aspartic acid in the PA helix (D79) and a lysine in the M2D helix (K1147) were proposed earlier to interact. Our results suggested individual roles of these residues in folding, structural integrity and function. While mutations of D79 completely abolished protein folding, mutations at position 1147 were tolerated to some extent. Intriguingly, a secondary interaction of D79 with R76 could enhance folding/stability of Trk1 and enable a fraction of Trk1[K1147A] to fold. The part of the ion permeation path containing the selectivity filter is shaped similar to that of ion channels. However below the selectivity filter it is obstructed or regulated by a proline containing loop. The presented model could provide the structural basis for addressing the long standing question if Trk1 is a passive or active ion-translocation system.
Institute of Pharmacology Medical University of Vienna Vienna Austria
Molecular Bioenergetics Institute of Cellular and Molecular Botany University of Bonn Bonn Germany
References provided by Crossref.org
Dimerisation of the Yeast K+ Translocation Protein Trk1 Depends on the K+ Concentration
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