Nematode chemoreceptor, Sra
Identifiers
SymbolSra_chemorcpt
PfamPF02117
InterProIPR000344
Available protein structures:
Pfam  structures / ECOD  
PDBRCSB PDB; PDBe; PDBj
PDBsumstructure summary

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. 1 2 3 4 5 6 Troemel ER, Chou JH, Dwyer ND, Colbert HA, Bargmann CI (October 1995). "Divergent seven transmembrane receptors are candidate chemosensory receptors in C. elegans". Cell. 83 (2): 207–218. doi:10.1016/0092-8674(95)90162-0. PMID 7585938.
  2. ↑ Robertson HM, Thomas JH (January 2006). "The putative chemoreceptor families of C. elegans". WormBook: 1–12. doi:10.1895/wormbook.1.66.1. PMC 4781013. PMID 18050473.
  3. ↑ Chen N, Pai S, Zhao Z, Mah A, Newbury R, Johnsen RC, et al. (January 2005). "Identification of a nematode chemosensory gene family". Proceedings of the National Academy of Sciences of the United States of America. 102 (1): 146–151. Bibcode:2005PNAS..102..146C. doi:10.1073/pnas.0408307102. PMC 539308. PMID 15618405.
  4. ↑ Nordström KJ, Sällman Almén M, Edstam MM, Fredriksson R, Schiöth HB (September 2011). "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. doi:10.1093/molbev/msr061. PMID 21402729.
  5. 1 2 Gühmann M, Porter ML, Bok MJ (August 2022). "The Gluopsins: Opsins without the Retinal Binding Lysine". Cells. 11 (15): 2441. doi:10.3390/cells11152441. PMC 9368030. PMID 35954284.
  6. ↑ Bownds D (December 1967). "Site of attachment of retinal in rhodopsin". Nature. 216 (5121): 1178–1181. Bibcode:1967Natur.216.1178B. doi:10.1038/2161178a0. PMID 4294735. S2CID 1657759.
  7. ↑ Collins FD (March 1953). "Rhodopsin and indicator yellow". Nature. 171 (4350): 469–471. Bibcode:1953Natur.171..469C. doi:10.1038/171469a0. PMID 13046517. S2CID 4152360.
  8. ↑ Pitt GA, Collins FD, Morton RA, Stok P (January 1955). "Studies on rhodopsin. VIII. Retinylidenemethylamine, an indicator yellow analogue". The Biochemical Journal. 59 (1): 122–128. doi:10.1042/bj0590122. PMC 1216098. PMID 14351151.
  9. ↑ Leung NY, Thakur DP, Gurav AS, Kim SH, Di Pizio A, Niv MY, Montell C (April 2020). "Functions of Opsins in Drosophila Taste". Current Biology. 30 (8): 1367–1379.e6. doi:10.1016/j.cub.2020.01.068. PMC 7252503. PMID 32243853.
  10. ↑ Kumbalasiri T, Rollag MD, Isoldi MC, Castrucci AM, Provencio I (March 2007). "Melanopsin triggers the release of internal calcium stores in response to light". Photochemistry and Photobiology. 83 (2): 273–279. doi:10.1562/2006-07-11-RA-964. PMID 16961436. S2CID 23060331.
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