Abstract
The acetylcholine-receptor protein (AchR) plays a key role in synaptic transmission because it controls the cation permeability of the postsynaptic membrane. It is an integral membrane glycoprotein of ≃ 3 x 105 daltons molecular weight, composed of several Polypeptide chains. Reports of its detailed chemical subunit composition and the number of ligandor neurotoxin binding sites are controversial [1, 2]. In purified postsynaptic membrane fragments (microsacs, see Fig. la) prepared from tissues rich in acetylcholine receptor, AchR is visualized by negative staining as densely packed round particles of ≃ 70 Å diameter [3,4,5,6], which are somewhat irregularly shaped (see also Fig. 1b). These particles possess a stain-filled central pit of ≃ 20 Å diameter. The terms “dough- nuts” or “rosettes” are often used to describe this appearance, which is due to a hydrated portion of AchR, protruding from the external surface of the microsac membrane by about 50 Å [6,7,8].
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Zingsheim, H.P., Neugebauer, DC., Barrantes, F.J., Frank, J. (1980). Image Averaging of Membrane-Bound Acetylcholine Receptor from Torpedo marmorata . In: Baumeister, W., Vogell, W. (eds) Electron Microscopy at Molecular Dimensions. Proceedings in Life Sciences. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-67688-8_19
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DOI: https://doi.org/10.1007/978-3-642-67688-8_19
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