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Updated: Aug 22, 2026

Comparing the Affinity of GTPase-binding Proteins using Competition Assays
Published on: October 8, 2015
Structural determinants of the PDE6 GAF A domain for binding the inhibitory gamma-subunit and noncatalytic cGMP
Hakim Muradov1, Kimberly K Boyd, Nikolai O Artemyev
1Department of Physiology and Biophysics, University of Iowa College of Medicine, 5-532 Bowen Science Bldg., 51 Newton Road, Iowa City, IA 52242, USA.
Abstract:
Photoreceptor cGMP phosphodiesterases (PDE6 family) are modular enzymes with each catalytic subunit containing two N-terminal regulatory GAF domains, GAF A and GAF B. The GAF A domains contribute to dimerization of the PDE6 catalytic subunits and to binding of the inhibitory Pgamma subunits, and represent candidate sites for noncatalytic binding of cGMP. We performed a mutational analysis of selected residues from the GAF A domain of cone PDEalpha' to identify the cGMP-binding pocket and delineate the Pgamma-binding surface. Results of this analysis establish the noncatalytic cGMP-binding site within the PDE6 GAF A domain and suggest that occupation of the pocket by cGMP is required for high-affinity binding of Pgamma to the proximate contact surface.
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