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The heteromeric cyclic nucleotide-gated channel adopts a 3A:1B stoichiometry


Cyclic nucleotide-gated (CNG) channels are crucial for visual and olfactory transductions1,2,3,4. These channels are tetramers and in their native forms are composed of A and B subunits5, with a stoichiometry thought to be 2A:2B (refs 6, 7). Here we report the identification of a leucine-zipper8-homology domain named CLZ (for carboxy-terminal leucine zipper). This domain is present in the distal C terminus of CNG channel A subunits but is absent from B subunits, and mediates an inter-subunit interaction. With cross-linking, non-denaturing gel electrophoresis and analytical centrifugation, this CLZ domain was found to mediate a trimeric interaction. In addition, a mutant cone CNG channel A subunit with its CLZ domain replaced by a generic trimeric leucine zipper produced channels that behaved much like the wild type, but less so if replaced by a dimeric or tetrameric leucine zipper. This A-subunit-only, trimeric interaction suggests that heteromeric CNG channels actually adopt a 3A:1B stoichiometry. Biochemical analysis of the purified bovine rod CNG channel confirmed this conclusion. This revised stoichiometry provides a new foundation for understanding the structure and function of the CNG channel family.

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Figure 1: Homotypic interaction of the C terminus of CNG channel A subunit.
Figure 2: Identification of the CLZ domain.
Figure 3: The CLZ domain forms a trimer.
Figure 4: Expression and functional properties of hCNGA3 and its CLZ-substituted mutants.
Figure 5: Analysis of the A and B subunits of the native rod CNG channel.


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We thank R. Huganir, P. Kim, D. Leahy, M. Li, J. Nathans, F. Rupp and D. Yue for advice and suggestions; members of the Yau laboratory for comments on the manuscript; M. Biel for the mCNGB3 cDNA; P. Kim for providing us with peptide samples corresponding to dimeric, trimeric and tetrameric leucine zippers; and M. Rodgers for helping us in the analytical centrifugation experiment. This work was supported by grants from the US National Eye Institute to K.-W.Y. and R.S.M.

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Correspondence to Robert S. Molday or King-Wai Yau.

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Zhong, H., Molday, L., Molday, R. et al. The heteromeric cyclic nucleotide-gated channel adopts a 3A:1B stoichiometry. Nature 420, 193–198 (2002).

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