Posts Tagged ‘channel’

Polarized object detection in crabs: a two-channel system [RESEARCH ARTICLE]

Melanie Ailin Basnak, Veronica Perez-Schuster, Gabriela Hermitte, and Martin Beron de AstradaMany animal species take advantage of polarization vision for vital tasks such as orientation, communication, and contrast enhancement. Previous studies have …

Activation mechanism of the calcium-activated chloride channel TMEM16A revealed by cryo-EM

The calcium-activated chloride channel TMEM16A is a ligand-gated anion channel that opens in response to an increase in intracellular Ca2+ concentration. The protein is broadly expressed and contributes to diverse physiological processes, including transepithelial chloride transport and the control of electrical signalling in smooth muscles and certain neurons. As a member of the TMEM16 (or anoctamin) family of membrane proteins, TMEM16A is closely related to paralogues that function as scramblases, which facilitate the bidirectional movement of lipids across membranes. The unusual functional diversity of the TMEM16 family and the relationship between two seemingly incompatible transport mechanisms has been the focus of recent investigations. Previous breakthroughs were obtained from the X-ray structure of the lipid scramblase of the fungus Nectria haematococca (nhTMEM16), and from the cryo-electron microscopy structure of mouse TMEM16A at 6.6 Å (ref. 14). Although the latter structure disclosed the architectural differences that distinguish ion channels from lipid scramblases, its low resolution did not permit a detailed molecular description of the protein or provide any insight into its activation by Ca2+. Here we describe the structures of mouse TMEM16A at high resolution in the presence and absence of Ca2+. These structures reveal the differences between ligand-bound and ligand-free states of a calcium-activated chloride channel, and when combined with functional experiments suggest a mechanism for gating. During activation, the binding of Ca2+ to a site located within the transmembrane domain, in the vicinity of the pore, alters the electrostatic properties of the ion conduction path and triggers a conformational rearrangement of an α-helix that comes into physical contact with the bound ligand, and thereby directly couples ligand binding and pore opening. Our study describes a process that is unique among channel proteins, but one that is presumably general for both functional branches of the TMEM16 family.

Chinese scientists build the first quantum satellite network

A Chinese satellite placed into orbit last summer has successfully used the laws of quantum mechanics to transmit information to Earth using an essentially unbreakable communications channel, according to BBC News and Los Angeles Times reports published Thursday. The experimental satellite known as Micius was launched from the Gobi desert in August 2016, and it […]

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Hubert Yockey, 1916-2016, and His Contributions to the Intelligent Design Movement

I was sad to recently realize that Hubert Yockey passed earlier (in January) this year. Hubert Yockey, though he personally was against Intelligent Design, made many contributions to science that many of us within the ID community view as pro-ID work. I wanted to take a moment to appreciate and reflect on his contributions as […]

Intramolecular interactions that control voltage sensitivity in the jShak1 potassium channel from Polyorchis penicillatus [RESEARCH ARTICLE]

Nazlee Sharmin and Warren J. GallinVoltage-gated potassium ion (Kv) channel proteins respond to changes in membrane potential by changing the probability of K+ flux through an ion-selective pore. Kv channels from different paralogous and orthologous fa…

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