Abstract
Phototransduction relies on the precise balance of speed and sensitivity to achieve optimal performance. The cyclic nucleotide-gated (CNG) ion channels, with their Ca(2+) permeability, high sensitivity to changes in cytosolic cGMP, rapid gating kinetics, and Ca(2+)-calmodulin modulation, are beautifully optimized for their role in light detection. Many of these specializations come about from the heteromeric composition of the native channel, comprised of CNGA1 and CNGB1 subunits. However, the stoichiometry and arrangement of these subunits is unknown. Here we have used an approach based on fluorescence resonance energy transfer (FRET) to determine the composition of the intact functional channel in the surface membrane. We find, surprisingly, that the channel contains three CNGA1 subunits and only one CNGB1 subunit. These results have implications for CNG channel function in particular and assembly of membrane proteins in general.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Calcium Signaling / physiology
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Calmodulin / metabolism
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Cattle
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Cyclic AMP / metabolism
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Cyclic GMP / metabolism
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Cyclic Nucleotide-Gated Cation Channels
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Fluorescence Resonance Energy Transfer
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Ion Channels / chemistry*
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Ion Channels / genetics
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Ion Channels / metabolism
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Luminescent Proteins / chemistry
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Luminescent Proteins / genetics
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Luminescent Proteins / metabolism
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Oocytes / physiology
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Patch-Clamp Techniques
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Protein Subunits / chemistry*
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Protein Subunits / genetics
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Protein Subunits / metabolism
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Recombinant Fusion Proteins / chemistry
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Recombinant Fusion Proteins / genetics
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Recombinant Fusion Proteins / metabolism
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Retinal Rod Photoreceptor Cells / chemistry*
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Retinal Rod Photoreceptor Cells / metabolism
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Vision, Ocular / physiology*
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Xenopus laevis
Substances
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Calmodulin
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Cyclic Nucleotide-Gated Cation Channels
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Ion Channels
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Luminescent Proteins
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Protein Subunits
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Recombinant Fusion Proteins
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Cyclic AMP
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Cyclic GMP