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Updated: May 25, 2026

Imaging Ca2+ Dynamics in Cone Photoreceptor Axon Terminals of the Mouse Retina
Published on: May 6, 2015
Comparative analysis of cone and rod transducins using chimeric Gα subunits
Kota N Gopalakrishna1, Kimberly K Boyd, Nikolai O Artemyev
1Department of Molecular Physiology and Biophysics, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242, United States.
None:
The molecular nature of transducin-α subunits (Gα(t)) may contribute to the distinct physiology of cone and rod photoreceptors. Biochemical properties of mammalian cone Gα(t2) subunits and their differences with rod Gα(t1) are largely unknown. Here, we examined properties of chimeric Gα(t2) in comparison with its rod counterpart. The key biochemical difference between the rod- and cone-like Gα(t) was ~10-fold higher intrinsic nucleotide exchange on the chimeric Gα(t2). Presented mutational analysis suggests that weaker interdomain interactions between the GTPase (Ras-like) domain and the helical domain in Gα(t2) are in part responsible for its increased spontaneous nucleotide exchange. However, the rates of R*-dependent nucleotide exchange of chimeric Gα(t2) and Gα(t1) were equivalent. Furthermore, chimeric Gα(t2) and Gα(t1) exhibited similar rates of intrinsic GTPase activity as well as similar acceleration of GTP hydrolysis by the RGS domain of RGS9. Our results suggest that the activation and inactivation properties of cone and rod Gα(t) subunits in an in vitro reconstituted system are comparable.
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