Torpedo complex subunits

Xu et al. [5] described the effect of (z>)-penicillamine on the binding of several antiacetylcholine receptor monoclonal antibodies to the Torpedo acetylcholine receptor. Penicillamine is covalently incorporated into the acetylcholine receptor through SS exchange at the cysteine residues of the a-subunit, altering the antigenic structure of the receptor. This effect on the structure of the native receptor at the neuromuscular junction may be responsible for the establishment of the autoimmune response to the acetylcholine receptor in (i))-penicillamine-induced myasthenia gravis. Cysteine and penicillamine interact to form penicillamine-cysteine mixed disulfide complexes [6] ... 

M2 exhibits high homology both between subunits of the Torpedo AChR a2PyS complex and between species (3). Secondary structure predictors suggest that M2 8 segments could form amphipathic a-helices (( x) = 0.25). 

Figure 30-23 The nicotinic acetylcholine receptor from the Torpedo ray. (A) The mouth of the receptor channel viewed from the synaptic cleft based on reconstruction from cryoEm images. Addition of acetylcholine, which binds to the two a subunits, induces small rotations in the five subunits of the 2Py5 complex causing the channel to open. From Unwin.

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