Purification and Cloning of Toxins from Elapid Venoms that Target Cyclic Nucleotide-Gated Ion Channels†,‡

Biochemistry ◽  
2002 ◽  
Vol 41 (38) ◽  
pp. 11331-11337 ◽  
Author(s):  
Yasuo Yamazaki ◽  
R. Lane Brown ◽  
Takashi Morita
Keyword(s):  
Ion Channels ◽  
Cyclic Nucleotide ◽  
Gated Ion Channels

scholarly journals Modification of Cyclic Nucleotide–Gated Ion Channels by Ultraviolet Light

2000 ◽  
Vol 116 (2) ◽  
pp. 227-252 ◽  
Author(s):  
Thomas R. Middendorf ◽  
Richard W. Aldrich ◽  
Denis A. Baylor
Keyword(s):  
Absorption Spectrum ◽  
Ion Channels ◽  
Ultraviolet Light ◽  
Cyclic Nucleotide ◽  
Uv Light ◽  
Action Spectrum ◽  
Light Sensitivity ◽  
Current Reduction ◽  
Photochemical Modification ◽  
Gated Ion Channels

We irradiated cyclic nucleotide–gated ion channels in situ with ultraviolet light to probe the role of aromatic residues in ion channel function. UV light reduced the current through excised membrane patches from Xenopus oocytes expressing the α subunit of bovine retinal cyclic nucleotide–gated channels irreversibly, a result consistent with permanent covalent modification of channel amino acids by UV light. The magnitude of the current reduction depended only on the total photon dose delivered to the patches, and not on the intensity of the exciting light, indicating that the functionally important photochemical modification(s) occurred from an excited state reached by a one-photon absorption process. The wavelength dependence of the channels' UV light sensitivity (the action spectrum) was quantitatively consistent with the absorption spectrum of tryptophan, with a small component at long wavelengths, possibly due to cystine absorption. This spectral analysis suggests that UV light reduced the currents at most wavelengths studied by modifying one or more “target” tryptophans in the channels. Comparison of the channels' action spectrum to the absorption spectrum of tryptophan in various solvents suggests that the UV light targets are in a water-like chemical environment. Experiments on mutant channels indicated that the UV light sensitivity of wild-type channels was not conferred exclusively by any one of the 10 tryptophan residues in a subunit. The similarity in the dose dependences of channel current reduction and tryptophan photolysis in solution suggests that photochemical modification of a small number of tryptophan targets in the channels is sufficient to decrease the currents.

scholarly journals Explorations of Lipid Effects in Cyclic Nucleotide-Gated Ion Channels using a Nanodisc Platform

2015 ◽  
Vol 108 (2) ◽  
pp. 290a-291a
Author(s):  
Alexis Jaramillo Cartagena ◽  
Crina Nimigean ◽  
Julia Kowal ◽  
Henning Stahlberg
Keyword(s):  
Ion Channels ◽  
Cyclic Nucleotide ◽  
Gated Ion Channels

scholarly journals Cyclic Nucleotide-Gated Ion Channels

2002 ◽  
Vol 82 (3) ◽  
pp. 769-824 ◽  
Author(s):  
U. Benjamin Kaupp ◽  
Reinhard Seifert
Keyword(s):  
Ion Channels ◽  
Sensory Neurons ◽  
Cyclic Nucleotide ◽  
Cation Channels ◽  
Voltage Gated ◽  
Nonselective Cation Channels ◽  
Retinal Photoreceptors ◽  
Cng Channel ◽  
B Subunits ◽  
Gated Ion Channels

Cyclic nucleotide-gated (CNG) channels are nonselective cation channels first identified in retinal photoreceptors and olfactory sensory neurons (OSNs). They are opened by the direct binding of cyclic nucleotides, cAMP and cGMP. Although their activity shows very little voltage dependence, CNG channels belong to the superfamily of voltage-gated ion channels. Like their cousins the voltage-gated K+ channels, CNG channels form heterotetrameric complexes consisting of two or three different types of subunits. Six different genes encoding CNG channels, four A subunits (A1 to A4) and two B subunits (B1 and B3), give rise to three different channels in rod and cone photoreceptors and in OSNs. Important functional features of these channels, i.e., ligand sensitivity and selectivity, ion permeation, and gating, are determined by the subunit composition of the respective channel complex. The function of CNG channels has been firmly established in retinal photoreceptors and in OSNs. Studies on their presence in other sensory and nonsensory cells have produced mixed results, and their purported roles in neuronal pathfinding or synaptic plasticity are not as well understood as their role in sensory neurons. Similarly, the function of invertebrate homologs found in Caenorhabditis elegans, Drosophila,and Limulus is largely unknown, except for two subunits of C. elegans that play a role in chemosensation. CNG channels are nonselective cation channels that do not discriminate well between alkali ions and even pass divalent cations, in particular Ca2+. Ca2+ entry through CNG channels is important for both excitation and adaptation of sensory cells. CNG channel activity is modulated by Ca2+/calmodulin and by phosphorylation. Other factors may also be involved in channel regulation. Mutations in CNG channel genes give rise to retinal degeneration and color blindness. In particular, mutations in the A and B subunits of the CNG channel expressed in human cones cause various forms of complete and incomplete achromatopsia.

scholarly journals Dissecting Intersubunit Contacts in Cyclic Nucleotide-Gated Ion Channels

Neuron ◽  
2002 ◽  
Vol 33 (5) ◽  
pp. 703-713 ◽  
Author(s):  
Tamara Rosenbaum ◽  
Sharona E. Gordon
Keyword(s):  
Ion Channels ◽  
Cyclic Nucleotide ◽  
Gated Ion Channels
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