title: Dynamics of Dangling Bonds of Water Molecules in pharaonis Halorhodopsin during Chloride Ion Transportation.
abstract: Ion transportation via the chloride ion pump protein pharaonis halorhodopsin (pHR) occurs through the sequential formation of several intermediates during a photocyclic reaction. Although the structural details of each intermediate state have been studied, the role of water molecules in the translocation of chloride ions inside of the protein at physiological temperatures remains unclear. To analyze the structural dynamics of water inside of the protein, we performed time-resolved Fourier transform infrared (FTIR) spectroscopy under H2O or H2(18)O hydration and successfully assigned water O-H stretching bands. We found that a dangling water band at 3626 cm(-1) in pHR disappears in the L1 and L2 states. On the other hand, relatively intense positive bands at 3605 and 3608 cm(-1) emerged upon the formation of the X(N) and O states, respectively, suggesting that the chloride transportation is accompanied by dynamic rearrangement of the hydrogen-bonding network of the internal water molecules in pHR.
authors: †Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan.|‡Department of Structural Molecular Science, The Graduate University for Advanced Studies (SOKENDAI), 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan.
authors: Yuji
authors: Y
authors: Furutani
authors: †Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan.|‡Department of Structural Molecular Science, The Graduate University for Advanced Studies (SOKENDAI), 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan.
authors: Kuniyo
authors: K
authors: Fujiwara
authors: †Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan.|‡Department of Structural Molecular Science, The Graduate University for Advanced Studies (SOKENDAI), 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan.
authors: Tetsunari
authors: T
authors: Kimura
authors: ¶Faculty of Advanced Life Science, Hokkaido University, Sapporo 060-0810, Japan.
authors: Takashi
authors: T
authors: Kikukawa
authors: ¶Faculty of Advanced Life Science, Hokkaido University, Sapporo 060-0810, Japan.
authors: Makoto
authors: M
authors: Demura
authors: #Department of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan.
authors: Hideki
authors: H
authors: Kandori
keywords: hydrogen bond; ion pump; microbial rhodopsin; time-resolved FTIR spectroscopy; water