For the Membrane Interface, see Membrane Interface. For Transmembrane Signaling in General, see Transmembrane Signaling in General, Because of my surprise at the number of Amphioxus GPCRs, I decided to try and find when GPCRs first appeared in evolution. Google found 220,000 hits for "Eukaryotic GPCRs". PubMed found 39 hits for "Eukaryotic GPCRs". The Molecular History of Eukaryotic Life (Goog?) http://drnelson.utmem.edu/MHEL.index.html Good resource. "Seven transmembrane segment receptors are eukaryotic proteins." "Yeast have only 3 GPCRs: STE2, STE3 and GPR1. These are receptors for pheromone (STE2 and STE3) and a receptor that is induced during starvation. " "...the fungi have not exploited these useful receptors very much. They seem to be used for mating purposes and for sensing the concentration of glucose in the environment. " "The seven transmembrane receptors have a remarkable similarity to bacteriorhodopsin and halorhodopsin. These are a light driven proton pump and a light driven chloride pump from the archaebacteria Halobacterium salinarium (previously named halobium)." This seems to imply that the GPCRs have their evolutionary roots in the archaea but didn't become full-fledged GPCRs until evolution of the eukaryotes. Signaling systems of lower eukaryotes and their evolution http://www.ncbi.nlm.nih.gov/pubmed/18779059 Only abstract available online. I got the 132 page PDF through the library. Signaling receptome: a genomic and evolutionary perspective (PubMed) http://www.ncbi.nlm.nih.gov/pubmed/12815191 Only abstract available online. I got PDF from the library. Also discussed in Transmembrane Signaling in General. This article completely ignores prokaryote signaling. The single receptor which evolved at the single cell eukaryotic stage is the seven transmembrane (7TM) G-protein coupled receptor (GPCR). Although the article doesn't give estimates for the total number of all receptors, it does give a breakdown for the five types of GPCRs found in seven genomes. The totals obtained by adding all five types together are: Genome Number of Different GPCRs Yeast 3 Nematode 1000 Fruit Fly 260 Mosquito 270 Sea Squirt 210 Fish 570 Human 800 and from another source - Amphioxus Neurotransmitters Amphioxus 664 Eukaryotic vs. prokaryotic chemosensory systems (PubMed) Only abstract available online. I have PDF. |