The GLIC receptor is a
bacterial
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
(
Gloeobacter)
Ligand-gated Ion Channel,
homolog
In biology, homology is similarity due to shared ancestry between a pair of structures or genes in different taxa. A common example of homologous structures is the forelimbs of vertebrates, where the wings of bats and birds, the arms of prima ...
to the
nicotinic acetylcholine receptors
Nicotinic acetylcholine receptors, or nAChRs, are receptor polypeptides that respond to the neurotransmitter acetylcholine. Nicotinic receptors also respond to drugs such as the agonist nicotine. They are found in the central and peripheral n ...
. It is a proton-gated (the channel opens when it binds a proton, ion),
cation
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
-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
Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...
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).
The similarity of amino-acid sequence to the eukaryotic
LGIC
Ligand-gated ion channels (LICs, LGIC), also commonly referred to as ionotropic receptors, are a group of transmembrane ion-channel proteins which open to allow ions such as Na+, K+, Ca2+, and/or Cl− to pass through the membrane in res ...
s is not localized to any single or particular
tertiary
Tertiary ( ) is a widely used but obsolete term for the geologic period from 66 million to 2.6 million years ago.
The period began with the demise of the non-avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start ...
domain
Domain may refer to:
Mathematics
*Domain of a function, the set of input values for which the (total) function is defined
**Domain of definition of a partial function
**Natural domain of a partial function
**Domain of holomorphy of a function
* Do ...
, 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
at low pH values of 4-4.6 (GLIC being proton-gated).
See also
*
Cys-loop receptors The Cys-loop ligand-gated ion channel superfamily is composed of nicotinic acetylcholine, GABAA, GABAA-ρ, glycine, 5-HT3, and zinc-activated (ZAC) receptors. These receptors are composed of five protein subunits which form a pentameric arrang ...
*
Ion channel
Ion channels are pore-forming membrane proteins that allow ions to pass through the channel pore. Their functions include establishing a resting membrane potential, shaping action potentials and other electrical signals by gating the flow of io ...
*
Receptor (biochemistry)
In biochemistry and pharmacology, receptors are chemical structures, composed of protein, that receive and transduce signals that may be integrated into biological systems. These signals are typically chemical messengers which bind to a recept ...
References
External links
Electrophysiology
Ion channels
Ionotropic receptors
Molecular neuroscience
Neurochemistry
Protein families
{{transmembranereceptor-stub