1887

Abstract

The rat cytomegalovirus (RCMV) gene encodes a G protein-coupled receptor (GPCR), pR33, which possesses agonist-independent, constitutive signalling activity. To characterize this activity further, we generated a series of point and deletion mutants of pR33. Both expression of and signalling by the mutants was evaluated. Several point mutants were generated that contained modifications in the NRY motif. This motif, at aa 130–132 of pR33, is the counterpart of the common DRY motif of GPCRs, which is known to be involved in G protein coupling. We found that mutation of the asparagine residue within the NRY motif of pR33 (N) to aspartic acid resulted in a mutant (ND) with similar signalling characteristics to the wild-type (WT) protein, indicating that N is not the determinant of constitutive activity of pR33. Interestingly, a mutant carrying an alanine at aa 130 (NA) was severely impaired in G-mediated, constitutive activation of phospholipase C, whereas it displayed similar levels of activity to pR33 in G-mediated signalling. Another protein that contained a modified NRY motif, RA, did not show constitutive activity, whereas mutants YF and YA displayed similar activities to the WT receptor. This indicated that residue R is critical for pR33 function , whereas Y is not. Finally, we identified two consecutive arginines within the C-terminal tails of both pR33 and its homologue from human CMV, pUL33, which are important for correct cell-surface expression of these receptors.

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2004-04-01
2019-11-12
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