Lock and key theory of acetylcholine

Question

According to lock and key theory single molecule will fit into single receptor only. How does Acetylcholine will binds to both Nicotinic (ligand gated receptor) and muscarinic receptor (g protein receptor)?

If so, is that lock and key theory is wrong?

Answer 1

Ah, if only it were that simple.

Nicotinic receptors in and of themselves, are complex, in that there are different subunits that bind acetylcholine. In the muscarinic receptors there are at least five different types that are called M1 through M5.

So, the lock and key model, even though an oversimplification, is still a valid concept, and the fact that ACh binds to two different types of receptors ( and at least 7 different subunits), doesn’t invalidate the lock and key model.