title: Proton currents constrain structural models of voltage sensor activation.
abstract: The Hv1 proton channel is evidently unique among voltage sensor domain proteins in mediating an intrinsic 'aqueous' H+conductance (GAQ). Mutation of a highly conserved 'gating charge' residue in the S4 helix (R1H) confers a resting-state H+'shuttle' conductance (GSH) in VGCs and Ci VSP, and we now report that R1H is sufficient to reconstitute GSHin Hv1 without abrogating GAQ. Second-site mutations in S3 (D185A/H) and S4 (N4R) experimentally separate GSHand GAQgating, which report thermodynamically distinct initial and final steps, respectively, in the Hv1 activation pathway. The effects of Hv1 mutations on GSHand GAQare used to constrain the positions of key side chains in resting- and activated-state VS model structures, providing new insights into the structural basis of VS activation and H+transfer mechanisms in Hv1.
authors: Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, United States.|Medical College of Virginia Campus, Virginia Commonwealth University School of Medicine, Richmond, United States.
authors: Aaron L
authors: AL
authors: Randolph
authors: Department of Biochemistry, University of Oxford, Oxford, United Kingdom.
authors: Younes
authors: 0000-0003-1611-6692
authors: Y
authors: Mokrab
authors: Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, United States.|Medical College of Virginia Campus, Virginia Commonwealth University School of Medicine, Richmond, United States.
authors: Ashley L
authors: AL
authors: Bennett
authors: Department of Biochemistry, University of Oxford, Oxford, United Kingdom.
authors: Mark Sp
authors: 0000-0001-6360-7959
authors: MS
authors: Sansom
authors: Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, United States.|Medical College of Virginia Campus, Virginia Commonwealth University School of Medicine, Richmond, United States.
authors: Ian Scott
authors: 0000-0002-6432-4253
authors: IS
authors: Ramsey
mesh_terms: D057809:HEK293 Cells; D006801:Humans; D007473:Ion Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020125:Mutation, Missense; D018408:Patch-Clamp Techniques; D011487:Protein Conformation; D011522:Protons
chemical_list: D007473:Ion Channels; D050505:Mutant Proteins; D011522:Protons
keywords: biophysics; channel gating; membrane channels; none; protein structure; proton transport; structural biology; voltage sensor