| First Author | Kostenis E | Year | 1997 |
| Journal | J Biol Chem | Volume | 272 |
| Issue | 31 | Pages | 19107-10 |
| PubMed ID | 9235898 | Mgi Jnum | J:42013 |
| Mgi Id | MGI:894940 | Doi | 10.1074/jbc.272.31.19107 |
| Citation | Kostenis E, et al. (1997) The N-terminal extension of Galphaq is critical for constraining the selectivity of receptor coupling. J Biol Chem 272(31):19107-10 |
| abstractText | Characteristically, an individual member of the superfamily of G protein-coupled receptors can interact only with a limited number of the many structurally closely related G protein heterotrimers that are expressed within a cell. Interestingly, the N termini of two G protein alpha subunits, Galphaq and Galpha11, differ from those of other alpha subunits in that they display a unique, highly conserved six-amino acid extension. To test the hypothesis that this sequence element is critical for proper receptor recognition, we prepared a Galphaq deletion mutant (-6q) lacking these first six amino acids. The -6q construct (or wild type Galphaq as a control) was coexpressed (in COS-7 cells) with several different Gi/o- or Gs-coupled receptors, and ligand-induced increases in inositol phosphate production were determined as a measure of G protein activation. Whereas these receptors did not efficiently interact with wild type Galphaq, most of them gained the ability to productively couple to -6q. Additional experiments indicated that the observed functional promiscuity of -6q is not due to overexpression (as compared with wild type Galphaq) or to a lack of palmitoylation. We conclude that the N-terminal extension characteristic for Galphaq/11 proteins is critical for constraining the receptor coupling selectivity of these subunits, indicative of a novel mechanism by which the fidelity of receptor-G protein interactions can be regulated. |
