3swy
From Proteopedia
CNGA3 626-672 containing CLZ domain
Structural highlights
Disease[CNGA3_HUMAN] Achromatopsia;Cone rod dystrophy. The disease is caused by mutations affecting the gene represented in this entry. Defects in CNGA3 may be a cause of Leber congenital amaurosis (LCA), a severe dystrophy of the retina, typically becoming evident in the first years of life. Visual function is usually poor and often accompanied by nystagmus, sluggish or near-absent pupillary responses, photophobia, high hyperopia and keratoconus. Function[CNGA3_HUMAN] Visual signal transduction is mediated by a G-protein coupled cascade using cGMP as second messenger. This protein can be activated by cyclic GMP which leads to an opening of the cation channel and thereby causing a depolarization of cone photoreceptors. Induced a flickering channel gating, weakened the outward rectification in the presence of extracellular calcium, increased sensitivity for L-cis diltiazem and enhanced the cAMP efficacy of the channel when coexpressed with CNGB3 (By similarity). Essential for the generation of light-evoked electrical responses in the red-, green- and blue sensitive cones.[1] Publication Abstract from PubMedMolecular determinants of ion channel tetramerization are well characterized, but those involved in heteromeric channel assembly are less clearly understood. The heteromeric composition of native channels is often precisely controlled. Cyclic nucleotide-gated (CNG) channels from rod photoreceptors exhibit a 3:1 stoichiometry of CNGA1 and CNGB1 subunits that tunes the channels for their specialized role in phototransduction. Here we show, using electrophysiology, fluorescence, biochemistry, and X-ray crystallography, that the mechanism for this controlled assembly is the formation of a parallel 3-helix coiled-coil domain of the carboxy-terminal leucine zipper region of CNGA1 subunits, constraining the channel to contain three CNGA1 subunits, followed by preferential incorporation of a single CNGB1 subunit. Deletion of the carboxy-terminal leucine zipper domain relaxed the constraint and permitted multiple CNGB1 subunits in the channel. The X-ray crystal structures of the parallel 3-helix coiled-coil domains of CNGA1 and CNGA3 subunits were similar, suggesting that a similar mechanism controls the stoichiometry of cone CNG channels. Molecular mechanism for 3:1 subunit stoichiometry of rod cyclic nucleotide-gated ion channels.,Shuart NG, Haitin Y, Camp SS, Black KD, Zagotta WN Nat Commun. 2011 Aug 30;2:457. doi: 10.1038/ncomms1466. PMID:21878911[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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