Nicotinic acetylcholine receptors three-dimensional structure

Figure 9.3. Electron microscopy and electron crystallography of the nicotinic acetylcholine receptor (NAR). a NAR channels in liposome membranes. On the left, they are mostly randomly oriented (but some form a more regular pattern). On the right, a regularly packed two-dimensional crystal has formed. Such samples can be used to obtain a three-dimensional structure at low resolution by electron crystallography, b Electron crystallographic structure, represented as density contour maps. Left Top view. Middle, right Side view. The bilayer and the portions of the receptor protruding from it into both directions are visible. The arrow in the right frame points to the acetylcholine binding site.

A FIGURE 7-45 Three-dimensional structure of the nicotinic acetylcholine receptor, (a) Schematic cutaway model of the pentameric receptor in the membrane for clarity, the p subunit is not shown. Each subunit contains an M2 a helix (red) that faces the central pore. Aspartate and glutamate side chains at both ends of the M2 helices form two rings of negative charges that help exclude anions from and attract cations to the channel. The gate, which is opened by binding of acetylcholine, lies within the pore, (b) Top Cross section of the exoplasmic face of the... 

Van Wagoner, R.M., Jacobsen, R.B., Olivera, B.M., and Ireland, C.M. (2003) Characterization and three-dimensional structure determination of ijj-conotoxin Phif, a novel noncompetitive antagonist of nicotinic acetylcholine receptors. Biochemistry, 42, 6353-6362. 

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