| Popis: |
The fact that nearly all known serotonin receptor subtypes are single subunit proteins, members of the same gene superfamily (the G protein-coupled receptor or 7TM superfamily) and that most are intronless genes has helped accelerate the cloning of this receptor family. The fact that the amino acid sequences of different serotonin receptors are among the least homologous of any single biogenic amine receptor family has had the opposite effect upon our rate of progress. With the recent announcement that a serotonin 5-HT1B receptor gene has been isolated (Adham et al. 1992) genes representing five different pharmacologically defined subtypes - 5-HT1A, 5-HT1B, 5-HT1C, 5-HT1D and 5-HT2 - have been isolated and characterized. At least four other known or suspected subtypes - 5-HT3, 5-HT4, 5-HT1E and 5-HT1P - still remain to be cloned. At least one of these, the 5-HT3 receptor(s), is a member of the multisubunit ligand-gated ion channel superfamily and likely to be unrelated in structure to the 7TM receptors known at this time. |
