Emerging Concepts in Ion Channel Biophysics

85 / 119

Emerging Concepts in Ion Channel Biophysics Poster Abstracts
80
44-POS Board 44
Virtual Rescuing of CNGF547L Mutant Channel by Cyclic Nucleotide Analogues
Iliana I. Lozano-M., Estela Ruiz-Baca, Leticia Saucedo-Mendiola, Angelica Lopez-Rodriguez.
Fac. C. Quimicas UJED, Durango, Durango, Mexico.
Cyclic nucleotide-gated (CNG) channels are critical to the photo transduction cascade that
underlie in vertebrate vision. These channels open and close in response to light-induced changes
in the intracellular cyclic GMP concentration. Approximately, 75% of the mutations related to
achromatopsia, a retinal disorder with impaired color vision, are in the genes encoding CNG
channels. The F547L mutation is located at the cyclic nucleotide binding domain (CNBD) in the
CNG A3 subunit. This mutant channel reaches the plasma membrane, but it is not functional at
37 oC. Interestingly, its function is rescued at 27oC or by co-expressing CNG ß subunits;
nevertheless, apparent affinity to cGMP is increased, suggesting that correct folding of the
protein can be induced leading to the functional rescue of the channel.
We have modelled the human CNGA3 channel and the CNGA3F547L mutant using as template
the crystal structure of the C. elegans CNG channel. The model of the mutant suggests a
constriction of the structure due to formation of new hydrogen bonds. By docking, we also tested
the affinity of natural CNG channel ligands such as cGMP and cAMP along with twelve cyclic
nucleotide analogues. Supporting the increased apparent affinity for ligand, previously reported,
CNGA3F547L mutation induces the reduction in size and volume of CNBD, increasing the score
affinity for most of the ligands tested, except two molecules that we consider good candidates to
rescue the mutant channel function as they keep the same score affinity in the wild type and
mutant channel.