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The GAF Domain of the cGMP-Binding, cGMP-Specific Phosphodiesterase (PDE5) Is a Sensor and a Sink for cGMP

Biswas, Kabir Hassan and Sopory, Shailaja and Visweswariah, Sandhya S (2008) The GAF Domain of the cGMP-Binding, cGMP-Specific Phosphodiesterase (PDE5) Is a Sensor and a Sink for cGMP. In: Biochemistry, 47 (11). pp. 3534-3543.

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We describe here a novel sensor for cGMP based on the GAF domain of the cGMP-binding, cGMP-specific phosphodiesterase 5 (PDE5) using bioluminescence resonance energy transfer (BRET). The wild type GAFa domain, capable of binding cGMP with high affinity, and a mutant (GAFaF163A) unable to bind cGMP were cloned as fusions between GFP and Rluc for BRET2 assays. BRET2 ratios of the wild type GAFa fusion protein, but not GAFaF163A, increased in the presence of cGMP but not cAMP. Higher basal BRET2 ratios were observed in cells expressing the wild type GAFa domain than in cells expressing GAFaF163A. This was correlated with elevated basal intracellular levels of cGMP, indicating that the GAF domain could act as a sink for cGMP. The tandem GAF domains in full length PDE5 could also sequester cGMP when the catalytic activity of PDE5 was inhibited. Therefore, these results describe a cGMP sensor utilizing BRET2 technology and experimentally demonstrate the reservoir of cGMP that can be present in cells that express cGMP-binding GAF domain-containing proteins. PDE5 is the target for the anti-impotence drug sildenafil citrate; therefore, this GAF-BRET2 sensor could be used for the identification of novel compounds that inhibit cGMP binding to the GAF domain, thereby regulating PDE5 catalytic activity.

Item Type: Journal Article
Publication: Biochemistry
Publisher: American Chemical Society
Additional Information: Copyright of this article belongs to American Chemical Society.
Department/Centre: Division of Biological Sciences > Molecular Reproduction, Development & Genetics
Date Deposited: 04 Jun 2010 09:33
Last Modified: 19 Sep 2010 05:59
URI: http://eprints.iisc.ac.in/id/eprint/26800

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