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Mechanism of Calcium/Calmodulin Inhibition of Rod Cyclic Nucleotide-Gated Channels

Matthew C. Trudeau and William N. Zagotta
Proceedings of the National Academy of Sciences of the United States of America
Vol. 99, No. 12 (Jun. 11, 2002), pp. 8424-8429
Stable URL: http://www.jstor.org/stable/3059024
Page Count: 6
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Mechanism of Calcium/Calmodulin Inhibition of Rod Cyclic Nucleotide-Gated Channels
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Abstract

Rod cyclic nucleotide-gated (CNG) channels are heterotetramers comprised of both CNGA1 and CNGB1 subunits. Calcium/calmodulin (Ca2+/CaM) binds to a site in the N-terminal region of CNGB1 subunits and inhibits the opening conformational change in CNGA1/CNGB1 channels. Here, we show that polypeptides derived from an N-terminal region of CNGB1 form a specific interaction with polypeptides derived from a C-terminal region of CNGA1 that is distal to the cyclic nucleotide-binding domain. Deletion of the Ca2+/CaM-binding site from the N-terminal region of CNGB1 eliminated both Ca2+/CaM modulation of the channel and the intersubunit interaction. Furthermore, the interaction was disrupted by the presence of Ca2+/CaM. These results suggest that Ca2+/CaM-dependent inhibition of rod channels is caused by the direct binding of Ca2+/CaM to a site in the N-terminal region in CNGB1, which disrupts the interaction between this region and a distal C-terminal region of CNGA1. The mechanism underlying Ca2+/CaM modulation of rod channels is distinct from that in olfactory (CNGA2) CNG channels.

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