Structural properties determining low K
| Autor: | Hisao, Tsukamoto, Masahiro, Higashi, Hideyoshi, Motoki, Hiroki, Watanabe, Christian, Ganser, Koichi, Nakajo, Yoshihiro, Kubo, Takayuki, Uchihashi, Yuji, Furutani |
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| Rok vydání: | 2018 |
| Předmět: |
Spectrophotometry
Infrared Protein Conformation Sodium Hydrogen Bonding Molecular Dynamics Simulation Microscopy Atomic Force Biophysical Phenomena Mice Potassium Channels Tandem Pore Domain Cations Liposomes Spectroscopy Fourier Transform Infrared Potassium Animals Quantum Theory Molecular Biophysics |
| Zdroj: | The Journal of biological chemistry. 293(18) |
| ISSN: | 1083-351X |
| Popis: | Canonical K(+) channels are tetrameric and highly K(+)-selective, whereas two-pore–domain K(+) (K2P) channels form dimers, but with a similar pore architecture. A two-pore–domain potassium channel TWIK1 (KCNK1 or K2P1) allows permeation of Na(+) and other monovalent ions, resulting mainly from the presence of Thr-118 in the P1 domain. However, the mechanistic basis for this reduced selectivity is unclear. Using ion-exchange–induced difference IR spectroscopy, we analyzed WT TWIK1 and T118I (highly K(+)-selective) and L228F (substitution in the P2 domain) TWIK1 variants and found that in the presence of K(+) ions, WT and both variants exhibit an amide-I band at 1680 cm(−1). This band corresponds to interactions of the backbone carbonyls in the selectivity filter with K(+), a feature very similar to that of the canonical K(+) channel KcsA. Computational analysis indicated that the relatively high frequency for the amide-I band is well explained by impairment of hydrogen bond formation with water molecules. Moreover, concentration-dependent spectral changes indicated that the K(+) affinity of the WT selectivity filter was much lower than those of the variants. Furthermore, only the variants displayed a higher frequency shift of the 1680-cm(−1) band upon changes from K(+) to Rb(+) or Cs(+) conditions. High-speed atomic force microscopy disclosed that TWIK1's surface morphology largely does not change in K(+) and Na(+) solutions. Our results reveal the local conformational changes of the TWIK1 selectivity filter and suggest that the amide-I bands may be useful “molecular fingerprints” for assessing the properties of other K(+) channels. |
| Databáze: | OpenAIRE |
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