A new subunit of the cyclic nucleotide-gated cation channel in retinal rods

Nature. 1993 Apr 22;362(6422):764-7. doi: 10.1038/362764a0.


Retinal rods respond to light with a membrane hyperpolarization produced by a G-protein-mediated signalling cascade that leads to cyclic GMP hydrolysis and the consequent closure of a cGMP-gated channel that is open in darkness. A protein that forms this channel has recently been purified from bovine retina and molecularly cloned, suggesting that the native cGMP-gated channel might be a homo-oligomer. Here we report the cloning of another protein from human retina which has only about 30% overall identity to the rod channel subunit. This protein, immunocytochemically localized to rod outer segments, does not form functional channels by itself. However, when co-expressed with the cloned human rod channel protein, it introduces rapid flickers to the channel openings that are characteristic of the native channel. The hetero-oligomeric channel is also highly sensitive to the blocker L-cis-diltiazem, like the native channel. This new protein thus seems to be another subunit of the native rod channel. The hetero-oligomeric nature of the rod channel means that it is no exception to a common motif shared by other ligand-gated channels.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Alternative Splicing
  • Amino Acid Sequence
  • Animals
  • Cell Line
  • Cloning, Molecular
  • Cyclic GMP / metabolism
  • Cyclic Nucleotide-Gated Cation Channels
  • Diltiazem / pharmacology
  • Electrochemistry
  • Eye Proteins / chemistry*
  • Eye Proteins / genetics
  • Humans
  • Immunoenzyme Techniques
  • Ion Channel Gating
  • Ion Channels / chemistry*
  • Ion Channels / genetics
  • Molecular Sequence Data
  • Rod Cell Outer Segment / chemistry*
  • Rod Cell Outer Segment / metabolism
  • Sequence Alignment
  • Transfection
  • Xenopus


  • Cyclic Nucleotide-Gated Cation Channels
  • Eye Proteins
  • Ion Channels
  • Diltiazem
  • Cyclic GMP