Biology:Nematode chemoreceptor
| Nematode chemoreceptor, Sra | |||||||||
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| Identifiers | |||||||||
| Symbol | Sra_chemorcpt | ||||||||
| Pfam | PF02117 | ||||||||
| InterPro | IPR000344 | ||||||||
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Nematode chemoreceptors are chemoreceptors of nematodes. Animals recognise a wide variety of chemicals using their senses of taste and smell. The nematode Caenorhabditis elegans has only 14 types of chemosensory neuron, yet is able to respond to dozens of chemicals because each neuron detects several stimuli. More than 40 highly divergent transmembrane proteins that could contribute to this functional diversity have been described.[1] Most of the candidate receptor genes are in clusters of similar genes; 11 of these appear to be expressed in small subsets of chemosensory neurons. A single type of neuron can potentially express at least 4 different receptor genes.[1] Some of these might encode receptors for water-soluble attractants, repellents and pheromones, which are divergent members of the G-protein-coupled receptor family.[1] Sequences of the Sra family of C. elegans receptor-like proteins contain 6-7 hydrophobic, putative transmembrane, regions. These can be distinguished from other 7TM proteins (especially those known to couple G-proteins) by their own characteristic TM signatures.
More than 1300 potential chemoreceptor genes have been identified in C. elegans, which are generally prefixed sr for serpentine receptor. The receptor superfamilies include Sra (Sra, Srb, Srab, Sre), Str (Srh, Str, Sri, Srd, Srj, Srm, Srn) and Srg (Srx, Srt, Srg, Sru, Srv, Srxa), as well as the families Srw, Srz, Srbc, Srsx and Srr.[1][2][3] Many of these proteins have homologues in Caenorhabditis briggsae.
These receptors are distantly related to the rhodopsin-like receptors.[4] In contrast the receptor Sro is a true rhodopsin-like receptor. It is a member of the nemopsins a subgroup of the opsins,[5] but unlike most other opsins it does not have a lysine corresponding to position 296 in cattle rhodopsin. The lysine is replaced by an asparagine.[1][5] The lysine is needed so that the chromophore retinal can covalently bind to the opsin[6] via a Schiff-base,[7][8] which makes the opsin light sensitive. If the lysine is replaced by another amino acid then the opsin becomes light insensitive.[9][10] Therefore, Sro is also thought to be a chemoreceptor.[1]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 "Divergent seven transmembrane receptors are candidate chemosensory receptors in C. elegans". Cell 83 (2): 207–218. October 1995. doi:10.1016/0092-8674(95)90162-0. PMID 7585938.
- ↑ "The putative chemoreceptor families of C. elegans". WormBook: 1–12. January 2006. doi:10.1895/wormbook.1.66.1. PMID 18050473.
- ↑ "Identification of a nematode chemosensory gene family". Proceedings of the National Academy of Sciences of the United States of America 102 (1): 146–151. January 2005. doi:10.1073/pnas.0408307102. PMID 15618405. Bibcode: 2005PNAS..102..146C.
- ↑ "Independent HHsearch, Needleman--Wunsch-based, and motif analyses reveal the overall hierarchy for most of the G protein-coupled receptor families". Molecular Biology and Evolution 28 (9): 2471–2480. September 2011. doi:10.1093/molbev/msr061. PMID 21402729.
- ↑ 5.0 5.1 "The Gluopsins: Opsins without the Retinal Binding Lysine". Cells 11 (15): 2441. August 2022. doi:10.3390/cells11152441. PMID 35954284.
- ↑ "Site of attachment of retinal in rhodopsin". Nature 216 (5121): 1178–1181. December 1967. doi:10.1038/2161178a0. PMID 4294735. Bibcode: 1967Natur.216.1178B.
- ↑ "Rhodopsin and indicator yellow". Nature 171 (4350): 469–471. March 1953. doi:10.1038/171469a0. PMID 13046517. Bibcode: 1953Natur.171..469C.
- ↑ "Studies on rhodopsin. VIII. Retinylidenemethylamine, an indicator yellow analogue". The Biochemical Journal 59 (1): 122–128. January 1955. doi:10.1042/bj0590122. PMID 14351151.
- ↑ "Functions of Opsins in Drosophila Taste". Current Biology 30 (8): 1367–1379.e6. April 2020. doi:10.1016/j.cub.2020.01.068. PMID 32243853.
- ↑ "Melanopsin triggers the release of internal calcium stores in response to light". Photochemistry and Photobiology 83 (2): 273–279. March 2007. doi:10.1562/2006-07-11-RA-964. PMID 16961436.
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