Cover picture: A single protomer of an archaeal glutamate transporter homologue GltPhR276S/M395R (PDB accession no. 4X2S) shown in the plane of the membrane. The positive charge of an arginine residue (green) located at the interface of the transport domain (light blue, yellow, and red) and trimerization domain (light brown) selects for anions and excludes cations through the transporter-associated chloride channel. The location of this positively charged residue also regulates the elevator movement required for transport (see Research Article by Cater et al., 13–24).
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Rhodopsin kinase and arrestin binding control the decay of photoactivated rhodopsin and dark adaptation of mouse rods
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.
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.
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.
Improved resolution of single channel dwell times reveals mechanisms of binding, priming, and gating in muscle AChR
Mukhtasimova et al. describe experimental modifications of the patch clamp technique that improve temporal resolution of currents through single acetylcholine receptor channels. The study not only distinguishes between the priming and gating steps, but it also reveals how rate and equilibrium constants change as a function of agonist occupancy.
Methods and Approaches
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.