Need info: ACH receptor conformation!

Keith Bradnam pdxkrb
Mon Dec 4 04:48:54 EST 1995


Jeremy Hamlet Bremen wrote...
>...How does the binding of one acetylcholine molecule to its post-synaptic 
> membrane receptor change the conformation of that receptor to improve the 
> binding affinity of a second acetylcholine molecule to the same receptor
> protein? 
>...

In a related family of receptors, the ionotropic glutamate receptors (iGluRs),
the binding of the neurotransmitter (glutamtate) occurs in a quite distinct
binding domain.  This domain seems to be bilobate in structure.   The ligand
binds to the larger lobe and this induces conformational changes so that the
second lobe closes around the ligand.  This has been termed the "venus fly
trap" model. After the ligand has been sequestered away, there are presumably
new residues that are available to make binding interactions.  The iGluRs are
also pentameric and also bind another ligand.  As I recall, one ligand has to
bind first which then makes a conformational change so that the second ligand
can bind.  Both of the binding domains have this bilobate structure.
Maybe something similar happens with the AChR.
O'Hara et al., Neuron, 11, pp. 41-52 is a good general reference on the nature
of these binding domains.

Hope this helps,

Keith




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