Strong cooperativity between subunits in voltage-gated proton channels.
Voltage-activated proton (Hv) channels are essential components in the innate immune response. Hv channels are dimeric proteins with one proton permeation pathway per subunit. It is unknown how Hv channels are activated by voltage and whether there is any cooperation between subunits during voltage activation. Using cysteine accessibility measurements and voltage-clamp fluorometry, we show data consistent with the possibility that the fourth transmembrane segment S4 functions as the voltage sensor in Ciona intestinalis Hv channels. Unexpectedly, in a dimeric Hv channel, the S4 in both subunits must move to activate the two proton permeation pathways. In contrast, if Hv subunits are prevented from dimerizing, the movement of a single S4 is sufficient to activate the proton permeation pathway in a subunit. These results indicate strong cooperativity between subunits in dimeric Hv channels.
Gonzalez
Carlos
C
Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, Florida, USA.
Koch
Hans P
HP
Drum
Ben M
BM
Larsson
H Peter
HP
D000818:Animals; D002938:Ciona intestinalis / Q000737:chemistry*; D003545:Cysteine; D031541:Fluorescence Resonance Energy Transfer; D005470:Fluorometry; D007113:Immunity, Innate / Q000502:physiology*; D007700:Kinetics; D018408:Patch-Clamp Techniques; D055503:Protein Multimerization; D021122:Protein Subunits / Q000378:metabolism*; D017494:Proton Pumps / Q000737:chemistry / Q000378:metabolism*
D021122:Protein Subunits; D017494:Proton Pumps; D003545:Cysteine