Delineation of Two Functionally Distinct γPDE Binding Sites on the Bovine Retinal cGMP Phosphodiesterase by a Mutant γPDE Subunit
Biochemistry(1998)
Abstract
The γ subunit of the retinal cGMP phosphodiesterase (γPDE) acts as an inhibitor of phosphodiesterase (PDE) catalytic activity and mediates enzyme regulation by the α subunit of the GTP-binding protein transducin (αT). In this work, we describe a full length, doubly point-mutated γ subunit, C68S, Y84C γPDE, which binds to PDE with increased affinity but has a decreased ability to inhibit the enzyme. Fluorescence studies monitoring the competition between wild-type γPDE and the C68S, Y84C γPDE mutant suggest that the mutant γPDE binds with high affinity to only half of the total sites occupied by wild-type γPDE. Competition studies between wild-type γPDE and the mutant further suggest that the wild-type protein is able to fully inhibit PDE activity even when the mutant γPDE occupies its high-affinity binding site on PDE. Taken together, our findings are consistent with a model in which there are two distinguishable binding sites for γPDE on the PDE enzyme but that only one of the two sites mediates PDE inhibition.
MoreTranslated text
Key words
bovine retinal cgmp phosphodiesterase,subunit
AI Read Science
Must-Reading Tree
Example
![](https://originalfileserver.aminer.cn/sys/aminer/pubs/mrt_preview.jpeg)
Generate MRT to find the research sequence of this paper
Chat Paper
Summary is being generated by the instructions you defined