Subunit interactions during cooperative opening of voltage-gated proton channels.
Voltage-gated proton (Hv1) channels are dimers, where each subunit has a separate permeation pathway. However, opening of the two pathways is highly cooperative. It is unclear how Hv1 channels open their permeation pathways, because Hv1 channels lack a classic pore domain. Using voltage-clamp fluorometry, we here detect two conformational changes reported by a fluorophore attached to the voltage sensor S4 in Hv1 channels. The first is voltage dependent and precedes channel opening, with properties consistent with reporting on independent S4 charge movements in the two subunits. The second is less voltage dependent and closely correlates with channel opening. Mutations that reduce dimerization or alter the intersubunit interface affect both the second conformational change and channel opening. These observations suggest that, following an initial S4 charge movement in the two subunits, there is a second, cooperative conformational change, involving interactions between subunits, that opens both pathways in Hv1 channels.
Department of Physiology and Biophysics, University of Miami, 1600 NW 10th Avenue, RMSB 5123, Miami, FL 33136, USA.
Feng
F
Qiu
Santiago
S
Rebolledo
Carlos
C
Gonzalez
H Peter
HP
Larsson
D000595:Amino Acid Sequence; D000818:Animals; D018118:Chloride Channels / Q000378:metabolism; D005260:Female; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology*; D007473:Ion Channels / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D024642:Potassium Channels, Voltage-Gated / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D011487:Protein Conformation; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism*; D015222:Sodium Channels / Q000378:metabolism; D014982:Xenopus laevis
D018118:Chloride Channels; C510235:HVCN1 protein, human; D007473:Ion Channels; D024642:Potassium Channels, Voltage-Gated; D021122:Protein Subunits; D015222:Sodium Channels