Table 1 |
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Taste and pheromone receptor gene (sub-)families in mice and Drosophila |
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| Receptor |
Number of intact genes |
Conservation* within each family |
Sites of expression |
Known ligands (examples) |
Structural notes |
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| Mouse/ human |
T1R |
3 (human) 3 (mouse) |
30-40% |
Taste cells in the tongue; T1R1 plus T1R3 or T1R2 plus T1R3 are preferentially coexpressed,
with few cells expressing all three genes |
Sweet chemicals (T1R2 plus T1R3) L-amino acids, umami chemicals (T1R1 plus T1R3) |
Similar to V2R (20-30% identical) |
| T2R |
28 (human); approximately 40 (mouse) |
25% to more than 80% |
Taste cells in the tongue; most cells express many, if not all, T2R genes |
Bitter compounds, such as cycloheximide (mouse T2R5), salicin (human T2R16), and PTC
(human T2R38) |
Similar to V1R (15-20% identical) |
|
| V1R |
5 (human) 137 (mouse) |
25% to nearly 100% |
Basal layer in the vomeronasal organ; probably one V1R gene expressed per cell |
2-heptanone (V1Rb1), 6-hydroxy-6-methyl-3-heptanone, n-pentylacetate, and isobutylamine |
Similar to T2R (15-20% identical); important for maternal aggression |
|
| V2R |
None in human; approximately 140 in mouse |
25% to nearly 100% |
Apical layer in the vomeronasal organ; probably one V2R gene expressed per cell |
None identified |
Similar to T1R (20-30% identical); forms a complex with MHC class Ib and β2-microglobulin;
may be required for aggression between males |
|
| MHC 1b |
None in human; 9 expressed in the mouse |
40% to more than 80% |
Apical layer in the vomeronasal organ; one or a few MHC 1b genes expressed per cell;
coexpressed with a V2R gene |
None (in the VNO) |
Forms a complex with β2-microglobulin and V2Rs; may be required for aggression between males |
|
| Fly |
GR |
69 |
Approximately 15-75% |
Spatially defined in one or several taste organs (labellum, labral and cibarial sense
organs, legs, wings, and female genitalia) |
Sugars and presumably other classes of compounds, including pheromones |
Distantly related to olfactory receptor genes (Or83b); gustatory receptor probably
recognize the whole spectrum of small soluble ligands; up to 20 subfamilies (with
1-8 genes each) |
| GR_S† |
8 |
44-75% |
Foreleg and labellum (Gr5a), possibly other taste sensory organs |
Trehalose (Gr5a) |
The knockout fly has lower sensitivity to trehalose; member of a subfamily of 7 genes |
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*The numbers in this column refer to amino-acid sequence identity in mice and amino-acid sequence similarity in Drosophila, respectively. †Indicates proposed rather than functionally established subfamilies of gustatory receptor genes that might function as sweet (S) receptors. This information is based on the functional characterization of a single receptor in this subfamily. |
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Matsunami and Amrein Genome Biology 2003 4:220 doi:10.1186/gb-2003-4-7-220 |
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