Sandbox Reserved 475: Difference between revisions
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Acetylcholine receptor proteins are present in the peripheral nervous system (PNS) as well as the central nervous system (CNS) in humans and many organisms, including invertebrates. The function of the receptor follows a general mechanism to which it is applied to almost any organism with a nervous system, that relies on the firing action potentials of the neurons.<ref>Guzman, F. Acetylcholine receptors: muscarinic and nicotinic. http://pharmacologycorner.com/acetylcholine-receptors-muscarinic-and-nicotinic/#what</ref> The structure depicted to the right is a redering of the the nicotinic acetylcholine receptor extracted from [http://en.wikipedia.org/wiki/Marbled_electric_ray Torpedo marmorata], more commonly known as the Marbled Electric Ray. Specifically, it is extracted from the electric organ's tissue from within the organism.<ref name="Refined">Unwin N. (March 4, 2005). "Refined structure of the nicotinic acetylcholine receptor at 4A resolution". Journal of Molecular Biology 346 (4): 967–89. doi:10.1016/j.jmb.2004.12.031. PMID 15701510.</ref> | Acetylcholine receptor proteins are present in the peripheral nervous system (PNS) as well as the central nervous system (CNS) in humans and many organisms, including invertebrates. The function of the receptor follows a general mechanism to which it is applied to almost any organism with a nervous system, that relies on the firing action potentials of the neurons.<ref>Guzman, F. Acetylcholine receptors: muscarinic and nicotinic. http://pharmacologycorner.com/acetylcholine-receptors-muscarinic-and-nicotinic/#what</ref> The structure depicted to the right is a redering of the the nicotinic acetylcholine receptor extracted from [http://en.wikipedia.org/wiki/Marbled_electric_ray Torpedo marmorata], more commonly known as the Marbled Electric Ray. Specifically, it is extracted from the electric organ's tissue from within the organism.<ref name="Refined">Unwin N. (March 4, 2005). "Refined structure of the nicotinic acetylcholine receptor at 4A resolution". Journal of Molecular Biology 346 (4): 967–89. doi:10.1016/j.jmb.2004.12.031. PMID 15701510.</ref> | ||
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== '''Mechanism''' == | == '''Mechanism''' == | ||
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In vertebrates, nicotinic receptors are classified by their main sites of expression into two subtypes: muscle-type nicotinic receptors and neuronal-type nicotinic receptors. In the muscle-type receptors, found at the neuromuscular junction, receptors are either the '''embryonic''' form, composed of '''α1''', '''β1''', '''δ''', and '''γ''' subunits in a '''2:1:1:1''' ratio, or the '''adult''' form composed of '''α1''', '''β1''', '''δ''', and '''ε''' subunits in a '''2:1:1:1''' ratio. The neuronal subtypes are various combinations of twelve different nicotinic receptor subunits: '''α2''' through '''α10''' and '''β2''' through '''β4'''. In both muscle-type and neuronal-type receptors, the subunits are somewhat similar to one another, especially in the hydrophobic regions. | In vertebrates, nicotinic receptors are classified by their main sites of expression into two subtypes: muscle-type nicotinic receptors and neuronal-type nicotinic receptors. In the muscle-type receptors, found at the neuromuscular junction, receptors are either the '''embryonic''' form, composed of '''α1''', '''β1''', '''δ''', and '''γ''' subunits in a '''2:1:1:1''' ratio, or the '''adult''' form composed of '''α1''', '''β1''', '''δ''', and '''ε''' subunits in a '''2:1:1:1''' ratio. The neuronal subtypes are various combinations of twelve different nicotinic receptor subunits: '''α2''' through '''α10''' and '''β2''' through '''β4'''. In both muscle-type and neuronal-type receptors, the subunits are somewhat similar to one another, especially in the hydrophobic regions. | ||
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<span style="font-size:110%"> | <span style="font-size:110%"> | ||
[[Image:Acetylcholine Binding.gif |left|350px|alt=text|Caption]] | [[Image:Acetylcholine Binding.gif |left|350px|alt=text|Caption]] | ||
As shown in the picture to the right, the two α-subunits are colored orange in this homeric receptor example. The two α-subunits each contain a ligand binding site colored red. '''Cys-192''' and '''Cys-193''', which are close proximity to the allosteric binding sites on the α-subunits for acetylcholine have been experimentally tested to show that disulfide residues provides stability in the binding of the neurotransmitter. The image (bottom left) shows a simplified depiction of the main components of one of the binding sites in a nAChR. Acetylcholine is shown to interact with various amino acid residues but specifically with the series of amino acids: Tyrosine (Y), Cysteine (C), Cysteine (C), and Tyrosine (Y). The cysteine sulfide residues form the disulfide interaction which aids in acetylcholine binding. The disulfide bonds facilitate the loop formations necessary for the appropriate bonds being formed with acetylcholine. | As shown in the picture to the right, the two α-subunits are colored orange in this homeric receptor example. The two α-subunits each contain a ligand binding site colored red. '''Cys-192''' and '''Cys-193''', which are close proximity to the allosteric binding sites on the α-subunits for acetylcholine have been experimentally tested to show that disulfide residues provides stability in the binding of the neurotransmitter.<ref name="Refined"/> The image (bottom left) shows a simplified depiction of the main components of one of the binding sites in a nAChR. Acetylcholine is shown to interact with various amino acid residues but specifically with the series of amino acids: Tyrosine (Y), Cysteine (C), Cysteine (C), and Tyrosine (Y). The cysteine sulfide residues form the disulfide interaction which aids in acetylcholine binding. The disulfide bonds facilitate the loop formations necessary for the appropriate bonds being formed with acetylcholine. | ||
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