title: Active water in protein-protein communication within the membrane: the case of SRII-HtrII signal relay.
abstract: We detect internal water molecules in a membrane-embedded receptor-transducer complex and demonstrate water structure changes during formation of the signaling state. Time-resolved FTIR spectroscopy reveals stimulus-induced repositioning of one or more structurally active water molecules to a significantly more hydrophobic environment in the signaling state of the sensory rhodopsin II (SRII)-transducer (HtrII) complex. These waters, distinct from bound water molecules within the SRII receptor, appear to be in the middle of the transmembrane interface region near the Tyr199(SRII)-Asn74(HtrII) hydrogen bond. We conclude that water potentially plays an important role in the SRII --> HtrII signal transfer mechanism in the membrane's hydrophobic core.
authors.affiliation: Department of Physics, Molecular Biophysics Laboratory, and Center for Photonics, Boston University, Boston, Massachusetts 02215, USA.
authors.forename: Vladislav B
authors.initials: VB
authors.lastname: Bergo
authors.forename: Elena N
authors.initials: EN
authors.lastname: Spudich
authors.forename: John L
authors.initials: JL
authors.lastname: Spudich
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Rothschild
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry* / Q000378:metabolism; D002462:Cell Membrane / Q000737:chemistry* / Q000378:metabolism; D025602:Halorhodopsins / Q000737:chemistry* / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D011485:Protein Binding / Q000502:physiology; D054730:Protein Interaction Domains and Motifs / Q000502:physiology*; D025603:Sensory Rhodopsins / Q000737:chemistry* / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D017550:Spectroscopy, Fourier Transform Infrared; D014867:Water / Q000737:chemistry* / Q000378:metabolism
chemical_list: D019843:Archaeal Proteins; D025602:Halorhodopsins; C100812:HtrII protein, Halobacterium salinarium; D025603:Sensory Rhodopsins; C061508:sensory rhodopsin II protein, archaeal; D014867:Water