Role of the conserved NPxxY(x)5,6F motif in the rhodopsin ground state and during activation
AUTOR(ES)
Fritze, Olaf
FONTE
The National Academy of Sciences
RESUMO
In the G protein-coupled receptor rhodopsin, the conserved NPxxY(x)5,6F motif connects the transmembrane helix VII and the cytoplasmic helix 8. The less geometrically constrained retinal analogue 9-demethyl-retinal prevents efficient transformation of rhodopsin to signaling metarhodopsin (Meta) II after retinal photoisomerization. Here, we demonstrate that Ala replacement mutations within the NPxxY(x)5,6F domain, which eliminate an interaction between aromatic residues Y306 and F313, allow formation of Meta II despite the presence of 9-demethyl-retinal. Also a disulfide bond linking residues 306 and 313 in the 9-demethyl-retinal-reconstituted mutant Y306C/F313C/C316S prevented Meta II formation, whereas the reduced form of the mutant readily transformed to Meta II after illumination. These observations suggest that the interaction between residues 306 and 313 is disrupted during the Meta I/Meta II transition. However, this enhancement in Meta II formation is not reflected in the G protein activation, which is dramatically reduced for these mutants, suggesting that changes in the Y306–F313 interaction also lead to a proper realigning of helix 8 after photoisomerization. The E134Q mutation, located in the second conserved motif, D(E)RY, rescues activity in 9-demethyl-retinal-reconstituted mutants to different degrees, depending on the position of the Ala replacement in the NPxxY(x)5,6F motif, thus revealing distinct roles for the NP and Y(x)5,6F portions. Our studies underscore the importance of the NPxxY(x)5,6F and D(E)RY motifs in providing structural constraints in rhodopsin that rearrange in response to photoisomerization during formation of the G protein-activating Meta II. The dual control of the structural rearrangements secures reliable transformation of quiescent rhodopsin to activating Meta II.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=151333Documentos Relacionados
- The Role of Dosage of the Region 7d1–7d5-6 of the X Chromosome in the Production of Homeotic Transformations in DROSOPHILA MELANOGASTER
- Molecular dynamic study of orotidine-5′-monophosphate decarboxylase in ground state and in intermediate state: A role of the 203–218 loop dynamics
- VERTICAL AND HORIZONTAL RESISTANCE OF F5:6 PROGENIES OF CAROTENOID-BIOFORTIFIED LETTUCE TO Bremia lactucae
- Synthesis of substituted 5-fluoro-5,6-dihydropyrimidines.
- Cytochrome P450/NADPH-dependent biosynthesis of 5,6-trans-epoxyeicosatrienoic acid from 5,6-trans-arachidonic acid