Xenbase Image ID: 127738

Figure 3. Functional characterization of CNGA1-GFP channels at the cell surface.A, B & C. Cysteine-less CNGA1-GFP channels. A, Ionic currents in the presence of saturating [cGMP] (2 mM). cGMP-activated currents shown were acquired in response to 100 ms voltage steps from −80 to +80 mV (every 20 mV) from a holding potential of 0 mV. B. Dose response for cGMP at +60 mV. Solid line represents a normalized Hill equation fit to the data. The best fit parameter values for K½ was 19±1 µM, and for the hill coefficient (n) was 2.1±0.2. Average values for K½ and n were 24±3 µM and 2.16±0.46, respectively (n = 4 oocytes). C. Efficacies for different agonists. Wild type CNGA1 channels displayed larger than 95% maximal probability of opening with saturated concentrations of cGMP, less with cIMP, and much less with cAMP. Nucleotide-activated current records shown were obtained from the same excised inside out patch with saturating concentrations of cGMP (2 mM; black), cIMP (16 mM; red) and cAMP (16 mM; blue). D, E & F. Rescued R272C CNGA1-GFP channels. D. Ionic current carried by MTSEA-modified R272C channels. In response to a comparable experimental protocol as in A, rescued channels were able to conduct ionic current with similar properties as wild type channels. E. Dose response of modified R272C channels at the cell surface for cGMP. Solid line corresponds to a normalized Hill equation fit to the data. The best fit parameter values for K½ and n were 43.4±2.5 µM and 1.9±0.3, respectively. Average values for K½ and n were 59±10 µM and 1.48±0.22, respectively (n = 14 oocytes). F. Agonist efficacies for rescued R272C mutant channels. Nucleotide-activated current records shown were acquired from the same patch, using the equivalent agonist concentration as in C. Similar observations were made in 3 different patches. Image published in: Lopez-Rodriguez A and Holmgren M (2012) Image downloaded from an Open Access article in PubMed Central. Image reproduced on Xenbase with permission of the publisher and the copyright holder. Larger Image Printer Friendly View

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