Journal article
Partial Reconstitution of Photoreceptor cGMP Phosphodiesterase Characteristics in cGMP Phosphodiesterase-5
The Journal of biological chemistry, Vol.276(24), pp.21698-21703
06/15/2001
DOI: 10.1074/jbc.M100626200
PMID: 11285263
Abstract
Photoreceptor cGMP phosphodiesterases (PDE6) are uniquely qualified to serve as effector enzymes in the vertebrate visual transduction cascade. In the dark-adapted photoreceptors, the activity of PDE6 is blocked via tight association with the inhibitory γ-subunits (Pγ). The Pγ block is removed in the light-activated PDE6 by the visual G protein, transducin. Transducin-activated PDE6 exhibits an exceptionally high catalytic rate of cGMP hydrolysis ensuring high signal amplification. To identify the structural determinants for the inhibitory interaction with Pγ and the remarkable cGMP hydrolytic ability, we sought to reproduce the PDE6 characteristics by mutagenesis of PDE5, a related cyclic GMP-specific, cGMP-binding PDE. PDE5 is insensitive to Pγ and has a more than 100-fold lower kcat for cGMP hydrolysis. Our mutational analysis of chimeric PDE5/PDE6α′ enzymes revealed that the inhibitory interaction of cone PDE6 catalytic subunits (PDE6α′) with Pγ is mediated primarily by three hydrophobic residues at the entry to the catalytic pocket, Met758, Phe777, and Phe781. The maximal catalytic rate of PDE5 was enhanced by at least 10-fold with substitutions of PDE6α′-specific glycine residues for the corresponding PDE5 alanine residues, Ala608 and Ala612. The Gly residues are adjacent to the highly conserved metal binding motif His-Asn-X-X-His, which is essential for cGMP hydrolysis. Our results suggest that the unique Gly residues allow the PDE6 metal binding site to adopt a more favorable conformation for cGMP hydrolysis.
Details
- Title: Subtitle
- Partial Reconstitution of Photoreceptor cGMP Phosphodiesterase Characteristics in cGMP Phosphodiesterase-5
- Creators
- Alexey E GranovskyNikolai O Artemyev
- Resource Type
- Journal article
- Publication Details
- The Journal of biological chemistry, Vol.276(24), pp.21698-21703
- DOI
- 10.1074/jbc.M100626200
- PMID
- 11285263
- NLM abbreviation
- J Biol Chem
- ISSN
- 0021-9258
- eISSN
- 1083-351X
- Publisher
- Elsevier Inc
- Language
- English
- Date published
- 06/15/2001
- Academic Unit
- Molecular Physiology and Biophysics; Iowa Neuroscience Institute; Ophthalmology and Visual Sciences
- Record Identifier
- 9984070472102771
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