Ca2+ permeation in cyclic nucleotide-gated channels.

Cyclic nucleotide-gated (CNG) channels conduct Na+, K+ and Ca2+ currents under the control of cGMP and cAMP. Activation of CNG channels leads to depolarization of the membrane voltage and to a concomitant increase of the cytosolic Ca2+ concentration. Several polypeptides were identified that constitute principal and modulatory subunits of CNG channels in both neurons and non-excitable cells, co-assembling to form a variety of heteromeric proteins with distinct biophysical properties.

Characterization of ether-à-go-go channels present in photoreceptors reveals similarity to IKx, a K+ current in rod inner segments.

In this study, we describe two splice variants of an ether-à-go-go (EAG) K+ channel cloned from bovine retina: bEAG1 and bEAG2. The bEAG2 polypeptide contains an additional insertion of 27 amino acids in the extracellular linker between transmembrane segments S3 and S4. The heterologously expressed splice variants differ in their activation kinetics and are differently modulated by extracellular Mg2+.

Novel caged compounds of hydrolysis-resistant 8-Br-cAMP and 8-Br-cGMP: photolabile NPE esters.

The application of the 1-(2-nitrophenyl)ethyl (NPE) moiety as a photolabile ligand for the release of hydrolysis-resistant 8-Br-cAMP and 8-Br-cGMP was examined. NPE-caged 8-Br-cAMP and 8-Br-cGMP liberate 8-Br-cAMP and 8-Br-cGMP during irradiation with ultraviolet light. The synthesis procedure resulted in diastereoisomeric mixtures, which were chromatographically separated into the axial and equatorial isomers of NPE-caged 8-Br-cAMP and 8-Br-cGMP.