Structural basis for activation of voltage sensor domains in an ion channel TPC1.

Autor: Kintzer AF; Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143., Green EM; Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143., Dominik PK; Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143.; Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637., Bridges M; Jules Stein Eye Institute, University of California, Los Angeles, CA 90095.; Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095., Armache JP; Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143., Deneka D; Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637., Kim SS; Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637., Hubbell W; Jules Stein Eye Institute, University of California, Los Angeles, CA 90095.; Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095., Kossiakoff AA; Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637., Cheng Y; Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143; YCheng@ucsf.edu stroud@msg.ucsf.edu.; Howard Hughes Medical Institute, University of California, San Francisco, CA 94143., Stroud RM; Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143; YCheng@ucsf.edu stroud@msg.ucsf.edu.
Jazyk: angličtina
Zdroj: Proceedings of the National Academy of Sciences of the United States of America [Proc Natl Acad Sci U S A] 2018 Sep 25; Vol. 115 (39), pp. E9095-E9104. Date of Electronic Publication: 2018 Sep 06.
DOI: 10.1073/pnas.1805651115
Abstrakt: Voltage-sensing domains (VSDs) couple changes in transmembrane electrical potential to conformational changes that regulate ion conductance through a central channel. Positively charged amino acids inside each sensor cooperatively respond to changes in voltage. Our previous structure of a TPC1 channel captured an example of a resting-state VSD in an intact ion channel. To generate an activated-state VSD in the same channel we removed the luminal inhibitory Ca 2+ -binding site (Ca i 2+ ), which shifts voltage-dependent opening to more negative voltage and activation at 0 mV. Cryo-EM reveals two coexisting structures of the VSD, an intermediate state 1 that partially closes access to the cytoplasmic side but remains occluded on the luminal side and an intermediate activated state 2 in which the cytoplasmic solvent access to the gating charges closes, while luminal access partially opens. Activation can be thought of as moving a hydrophobic insulating region of the VSD from the external side to an alternate grouping on the internal side. This effectively moves the gating charges from the inside potential to that of the outside. Activation also requires binding of Ca 2+ to a cytoplasmic site (Ca a 2+ ). An X-ray structure with Ca a 2+ removed and a near-atomic resolution cryo-EM structure with Ca i 2+ removed define how dramatic conformational changes in the cytoplasmic domains may communicate with the VSD during activation. Together four structures provide a basis for understanding the voltage-dependent transition from resting to activated state, the tuning of VSD by thermodynamic stability, and this channel's requirement of cytoplasmic Ca 2+ ions for activation.
Competing Interests: The authors declare no conflict of interest.
Databáze: MEDLINE
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