This (the green protein) is acetylcholinesterase. It is found in the space between neural synapses. The small blue guys are acetylcholine neurotransmitters, and are released from the pre-synaptic membrane of one neuron, and received by acetycholine receptors on the post-synaptic membrane of the next neuron, passing on the signal. acetylcholinesterase breaks down the acetylcholine in the synapse, and terminates the neurotransmission. The Red molecule is Donepezil, which is sometimes used to improve cognition in Alzheimer’s patients by inhibiting the acetylcholinesterase.
Donepezil is a reversible inhibitor which means that it is broken down in a few hours, and is useful for neural regulation. Other non-reversible inhibitors, such as those found in snake venom, take days to break down and can cause paralysis or asphyxiation. Another reversible inhibitor of acetylcholinesterase is tetrahydrocannibinol, or THC, the main psychoactive ingredient in cannabis.
I used pdb 4EY7 to model the Acetylcholinesterase.