Journal article
A Conformational Switch in the Inhibitory γ-Subunit of PDE6 upon Enzyme Activation by Transducin
Biochemistry (Easton), Vol.40(44), pp.13209-13215
11/06/2001
DOI: 10.1021/bi011127j
PMID: 11683629
Abstract
In response to light, a photoreceptor G protein, transducin, activates cGMP-phosphodiesterase (PDE6) by displacing the inhibitory γ-subunits (Pγ) from the enzyme's catalytic sites. Evidence suggests that the activation of PDE6 involves a conformational change of the key inhibitory C-terminal domain of Pγ. In this study, the C-terminal region of Pγ, Pγ-73−85, has been targeted for Ala-scanning mutagenesis to identify the point-to-point interactions between Pγ and the PDE6 catalytic subunits and to probe the nature of the conformational change. Pγ mutants were tested for their ability to inhibit PDE6 and a chimeric PDE5−conePDE6 enzyme containing the Pγ C-terminus-binding site of cone PDE. This analysis has revealed that in addition to previously characterized Ile86 and Ile87, important inhibitory contact residues of Pγ include Asn74, His75, and Leu78. The patterns of mutant PDE5−conePDE6 enzyme inhibition suggest the interaction between the PγAsn74/His75 sequence and Met758 of the cone PDE6α‘ catalytic subunit. This interaction, and the interaction between the PγIle86/Ile87 and PDE6α‘Phe777/Phe781 residues, is most consistent with an α-helical structure of the Pγ C-terminus. The analysis of activation of PDE6 enzymes containing Pγ mutants with Ala-substituted transducin-contact residues demonstrated the critical role of PγLeu76. Accordingly, we hypothesize that the initial step in PDE6 activation involves an interaction of transducin-α with PγLeu76. This interaction introduces a bend into the α-helical structure of the Pγ C-terminus, allowing transducin-α to further twist the C-terminus thereby uncovering the catalytic pocket of PDE6.
Details
- Title: Subtitle
- A Conformational Switch in the Inhibitory γ-Subunit of PDE6 upon Enzyme Activation by Transducin
- Creators
- Alexey E GranovskyNikolai O Artemyev
- Resource Type
- Journal article
- Publication Details
- Biochemistry (Easton), Vol.40(44), pp.13209-13215
- Publisher
- American Chemical Society
- DOI
- 10.1021/bi011127j
- PMID
- 11683629
- ISSN
- 0006-2960
- eISSN
- 1520-4995
- Language
- English
- Date published
- 11/06/2001
- Academic Unit
- Molecular Physiology and Biophysics; Iowa Neuroscience Institute; Ophthalmology and Visual Sciences
- Record Identifier
- 9984025349602771
Metrics
37 Record Views