Acetycholine esterase (AChE) "plays an important role in the regulation of functions of central and peripheral nervous systems. AChE hydrolyses the cationic neurotransmitter acetylcholine (ACh)" (Da Ros, 2006).
Curare poison, from the bark of a tree in South America, binds to the ACh receptors but doesn't activate them. To understand how this works is to think of it described "as a lock and a key ("lock and key model"). The neurotransmitter (the key) fits the receptor site (the lock). Some drugs act just like the key and attach to the receptor site, conveying a signal just like the neurotransmitter (e.g., nicotine). Other chemicals attach themselves to receptor sites but do not convey a message (e.g., the curare poison). This prevents the neurotransmitter itself from conveying the signal and is like a key that fits a lock but does not actually turn the lock, blocking the real key instead." (Palmer, 2003) This is further explained by the following diagram provided by J.K. Palmer at Eastern Kentucky University:
It has been found that organopesticides (OP) bind to acetylcholinesterase and inhibit its normal activity. This will affect muscle tissue by "targeting and depressing acetylcholinesterase activity in a dose-dependent manner, leading to an excessive acetylcholine output, nerve paralysis and finally death.