title: State-dependent network connectivity determines gating in a K+ channel.
abstract: X-ray crystallography has provided tremendous insight into the different structural states of membrane proteins and, in particular, of ion channels. However, the molecular forces that determine the thermodynamic stability of a particular state are poorly understood. Here we analyze the different X-ray structures of an inwardly rectifying potassium channel (Kir1.1) in relation to functional data we obtained for over 190 mutants in Kir1.1. This mutagenic perturbation analysis uncovered an extensive, state-dependent network of physically interacting residues that stabilizes the pre-open and open states of the channel, but fragments upon channel closure. We demonstrate that this gating network is an important structural determinant of the thermodynamic stability of these different gating states and determines the impact of individual mutations on channel function. These results have important implications for our understanding of not only K+ channel gating but also the more general nature of conformational transitions that occur in other allosteric proteins.
authors: Physiological Institute, Christian-Albrechts University, 24118 Kiel, Germany.
authors: Murali K
authors: MK
authors: Bollepalli
authors: Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK.
authors: Philip W
authors: PW
authors: Fowler
authors: Physiological Institute, Christian-Albrechts University, 24118 Kiel, Germany.
authors: Markus
authors: M
authors: Rapedius
authors: Clarendon Laboratory, Department of Physics, University of Oxford Oxford, OX1 3PU, UK.
authors: Lijun
authors: L
authors: Shang
authors: Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK; OXION Ion Channel Initiative, University of Oxford, Oxford OX1 3PT, UK.
authors: Mark S P
authors: MS
authors: Sansom
authors: Clarendon Laboratory, Department of Physics, University of Oxford Oxford, OX1 3PU, UK; OXION Ion Channel Initiative, University of Oxford, Oxford OX1 3PT, UK. Electronic address: stephen.tucker@physics.ox.ac.uk.
authors: Stephen J
authors: SJ
authors: Tucker
authors: Physiological Institute, Christian-Albrechts University, 24118 Kiel, Germany. Electronic address: t.baukrowitz@physiologie.uni-kiel.de.
authors: Thomas
authors: T
authors: Baukrowitz
mesh_terms: D000818:Animals; D018360:Crystallography, X-Ray; D005260:Female; D006863:Hydrogen-Ion Concentration; D015640:Ion Channel Gating / Q000235:genetics* / Q000502:physiology; D008958:Models, Molecular; D009154:Mutation; D009865:Oocytes / Q000378:metabolism / Q000502:physiology; D018408:Patch-Clamp Techniques; D024661:Potassium Channels, Inwardly Rectifying / Q000737:chemistry* / Q000235:genetics* / Q000502:physiology; D011487:Protein Conformation; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D051381:Rats; D013816:Thermodynamics; D014981:Xenopus
chemical_list: C510692:Kcnj1 protein, rat; D024661:Potassium Channels, Inwardly Rectifying; D021122:Protein Subunits