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Journal article
Mg2+/Ca2+ cation binding cycle of guanylyl cyclase activating proteins (GCAPs): role in regulation of photoreceptor guanylyl cyclase
Molecular and cellular biochemistry, v 334(1-2), pp 117-124
01 Jan 2010
PMID: 19953307
Featured in Collection : UN Sustainable Development Goals @ Drexel
Abstract
Photon absorption by photoreceptors activates hydrolysis of cGMP, which shuts down cGMP-gated channels and decreases free Ca(2+) concentrations in outer segment. Suppression of Ca(2+) influx through the cGMP channel by light activates retinal guanylyl cyclase through guanylyl cyclase activating proteins (GCAPs) and thus expedites photoreceptors recovery from excitation and restores their light sensitivity. GCAP1 and GCAP2, two ubiquitous among vertebrate species isoforms of GCAPs that activate retGC during rod response to light, are myristoylated Ca(2+)/Mg(2+)-binding proteins of the EF-hand superfamily. They consist of one non-metal binding EF-hand-like domain and three other EF-hands, each capable of binding Ca(2+) and Mg(2+). In the metal binding EF-hands of GCAP1, different point mutations can selectively block binding of Ca(2+) or both Ca(2+) and Mg(2+) altogether. Activation of retGC at low Ca(2+) (light adaptation) or its inhibition at high Ca(2+) (dark adaptation) follows a cycle of Ca(2+)/Mg(2+) exchange in GCAPs, rather than release of Ca(2+) and its binding by apo-GCAPs. The Mg(2+) binding in two of the EF-hands controls docking of GCAP1 with retGC1 in the conditions of light adaptation and is essential for activation of retGC. Mg(2+) binding in a C-terminal EF-hand contributes to neither retGC1 docking with the cyclase nor its subsequent activation in the light, but is specifically required for switching the cyclase off in the conditions of dark adaptation by binding Ca(2+). The Mg(2+)/Ca(2+) exchange in GCAP1 and 2 operates within different range of intracellular Ca(2+) concentrations and provides a two-step activation of the cyclase during rod recovery.
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Details
- Title
- Mg2+/Ca2+ cation binding cycle of guanylyl cyclase activating proteins (GCAPs): role in regulation of photoreceptor guanylyl cyclase
- Creators
- Alexander M Dizhoor - Salus UniversityElena V Olshevskaya - Salus UniversityIgor V Peshenko - Salus University
- Publication Details
- Molecular and cellular biochemistry, v 334(1-2), pp 117-124
- Publisher
- Springer Nature
- Grant note
- R01 EY011522-14 / NEI NIH HHS R01 EY011522 / NEI NIH HHS EY11522 / NEI NIH HHS
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Neurobiology and Anatomy; Pennsylvania College of Optometry (PCO)
- Web of Science ID
- WOS:000273593800009
- Scopus ID
- 2-s2.0-75049085185
- Other Identifier
- 991022035114404721
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- Cell Biology