- The anion/cation switch of the EAAT1 Cl− channel
Excitatory amino acid transporters possess a Cl− conductance whose direction is independent of that of the substrate. By mutating an arginine residue in the putative anion permeation pathway, Cater et al. show that a positive charge at this position determines anion selectivity.
- Patch-clamp fluorometry–based channel counting
The number of channels on a patch of membrane is a fundamental quantity for biophysical studies of ion channel mechanisms. Liu et al. develop a new method of channel counting based on patch-clamp fluorometry and use it to measure the single-channel conductance and ionic selectivity of HCN1 and HCN2 channels.
- Asn 14 mutant Cx26 hemichannels and KID syndrome
Mutations in connexin 26 hemichannels are the most common cause of congenital sensorineural hearing loss. Sanchez et al. investigate two mutations with disparate effects, N14K and N14Y, and find that the open state is stabilized in N14K channels.
- Role of Meta III decay in rod dark adaptation
G-protein receptor kinase and arrestin 1 are required for inactivation of photoactivated vertebrate rhodopsin. Frederiksen et al. show that they additionally regulate the subsequent decay of inactive rhodopsin into opsin and all-trans retinal and therefore dark adaptation.
- Electrophysiological characterization of NCX_Mj
NCX_Mj is a sodium–calcium exchanger from the archaebacterium Methanococcus jannaschii, whose crystal structure has been solved. Barthmes et al. use solid supported membrane–based electrophysiology to characterize NCX_Mj and reveal its functional similarity to eukaryotic isoforms.
- Structurally distinct open states of TREK-2
TREK channels, which are gated open by a wide range of stimuli, exist in at least two conformations known as “up” and “down.” McClenaghan et al. show that the channel can be open in both of these conformations and that gating is primarily achieved by the channel’s selectivity filter.
- Structural determinants of CaV1.1 gating
CaV1.1 is a slowly activating voltage-gated Ca2+ channel that exists in two splice variants with different voltage sensitivities. By making chimeras of these variants, Tuluc et al. show that activation kinetics and voltage dependence are controlled by distinct molecular mechanisms in the voltage-sensing domains of repeats I and IV, respectively.
- P2X7-like currents mediated by TRPM7
Extracellular ATP activates receptors such as P2X ligand-gated ion channels, but it also chelates divalent cations. Nörenberg et al. find that experimental conditions designed to measure P2X7 activity also activate TRPM7 channels, by relieving inhibition by extracellular divalent cations, in HEK293 and rat C6 glioma cells.
- Exceptionally high reactivity of TRPA1 Cys
Electrophiles produced during oxidative stress trigger pain responses by reacting with TRPA1 ion channels on sensory nerves. Bahia et al. show that residue C621 on TRPA1 has remarkable reactivity with electrophiles—more than cellular antioxidants—and is crucial for this sensory response.