From hopanoids to cholesterol: Molecular clocks of pentameric ligand-gated ion channels

Pentameric ligand-gated ion channels (pLGICs) and their lipid microenvironments appear to have acquired mutually adaptive traits along evolution: 1) the three-ring architecture of their transmembrane (TM) region; 2) the ability of the outermost TM ring to convey lipid signals to the middle ring, whi...

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Bibliographic Details
Published in:Progress in lipid research 2016-07, Vol.63, p.1-13
Main Authors: Barrantes, Francisco J., Fantini, Jacques
Format: Article
Language:English
Subjects:
Bacterial Proteins - chemistry
Bacterial Proteins - metabolism
Biological Clocks - physiology
Cholesterol
Cholesterol - metabolism
Cyanobacteria - metabolism
Erwinia
Evolution
Gloeobacter
Hopanoids
Ion channel evolution
Ligand-Gated Ion Channels - chemistry
Ligand-Gated Ion Channels - metabolism
Pectobacterium chrysanthemi - metabolism
Pentameric ligand-gated ion channels
Protein Binding
Protein Structure, Quaternary
Steroids
Triterpenes - chemistry
Triterpenes - metabolism
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Summary:Pentameric ligand-gated ion channels (pLGICs) and their lipid microenvironments appear to have acquired mutually adaptive traits along evolution: 1) the three-ring architecture of their transmembrane (TM) region; 2) the ability of the outermost TM ring to convey lipid signals to the middle ring, which passes them on to the central pore ring, and 3) consensus motifs for sterol recognition in all pLGICs. Hopanoids are triterpenoid fossil lipids that constitute invaluable biomarkers for tracing evolution at the molecular scale. The cyanobacterium Gloeobacter violaceus is the oldest known living organism in which the X-ray structure of its pLGIC, GLIC, reveals the presence of the above attributes and, as discussed in this review, the ability to bind hopanoids. ELIC, the pLGIC from the bacillus Erwinia chrysanthemi is the only other known case to date. Both prokaryotes lack cholesterol but their pLGICs exhibit the same sterol motifs as mammalian pLGIC. This remarkable conservation suggests that the association of sterols and hopanoid surrogate molecules arose from the early need in prokaryotes to stabilize pLGIC TM regions by means of relatively rigid lipid molecules. The conservation of these phenotypic traits along such a long phylogenetic span leads us to suggest the possible co-evolution of these sterols with pLGICs.
ISSN:0163-7827
1873-2194
DOI:10.1016/j.plipres.2016.03.003