Biology:GLIC
The GLIC receptor is a bacterial (Gloeobacter) Ligand-gated Ion Channel, homolog to the nicotinic acetylcholine receptors. It is a proton-gated (the channel opens when it binds a proton, H+ ion), cation-selective channel (it selectively lets the positive ions through). Like the nicotinic acetylcholine receptors is a functional pentameric oligomer (the channel normally works as an assembly of five subunits). However while its eukaryotic homologues are hetero-oligomeric (assembled from different subunits), all until now known bacteria known to express LICs encode a single monomeric unit, indicating the GLIC to be functionally homo-oligomeric (assembled from identical subunits).[1] The similarity of amino-acid sequence to the eukaryotic LGICs is not localized to any single or particular tertiary domain, indicating the similar function of the GLIC to its eukaryotic equivalents. Regardless, the purpose of regulating the threshold for action potential excitation in the nerve signal transmission of multicellular organisms cannot translate to single-cell organisms, thereby not making the purpose of bacterial LGICs immediately obvious.
Structure
The structure of the open channel structure was solved by two independent research teams in 2009[2][3] at low pH values of 4-4.6 (GLIC being proton-gated).
See also
- Cys-loop receptors
- Ion channel
- Receptor (biochemistry)
References
- ↑ "Identification of the prokaryotic ligand-gated ion channels and their implications for the mechanisms and origins of animal Cys-loop ion channels". Genome Biology 6 (1): R4. 2004. doi:10.1186/gb-2004-6-1-r4. ISSN 1465-6906. PMID 15642096.
- ↑ "X-ray structure of a pentameric ligand-gated ion channel in an apparently open conformation". Nature 457 (7225): 111–114. 2009. doi:10.1038/nature07462. ISSN 0028-0836. PMID 18987633. Bibcode: 2009Natur.457..111B.
- ↑ "Structure of a potentially open state of a proton-activated pentameric ligand-gated ion channel". Nature 457 (7225): 115–U122. 2009. doi:10.1038/nature07461. ISSN 0028-0836. PMID 18987630. Bibcode: 2009Natur.457..115H.
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