Sandbox Reserved 475: Difference between revisions

== <span style="font-size:120%">ACETYLCHOLINE RECEPTOR</span> ==

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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. 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. 

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Nicotinic Acetylcholine Receptor is composed up five distinct subunits (shown in figure to left): α1, α2, β1, δ, and ε at approximately a molecular mass of 290 kDa. The subunits are symmetrically arranged around a central pore. Each subunit is a transmembrane domain with the N-terminus and C-terminus located on the extracellular side of the plasma membrane. Each subunit are composed of long protein chains that extend across the cell membrane. The subunits have a composition of around ~20% beta sheets and ~40% alpha helices from about ~370 residues in total.  

<span style="font-size:110%">[[Image:2bg9 composite.gif |right|130px|alt=text|Caption]]  

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. As shown in the picture, 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 to the binding sites on the α-subunits have been experimentally tested to show that disulfide