<Li> Ligand (such as acetylcholine) </Li> <P> Acetylcholine is a neurotransmitter synthesized from dietary choline and acetyl - CoA (ACoA), and is involved in the stimulation of muscle tissue in vertebrates as well as in some invertebrate animals . In vertebrate animals, the acetylcholine receptor subtype that is found at the neuromuscular junction of skeletal muscles is the nicotinic acetylcholine receptor (nAChR), which is a ligand - gated ion channel . Each subunit of this receptor has a characteristic "cys - loop," which is composed of a cysteine residue followed by 13 amino acid residues and another cysteine residue . The two cysteine residues form a disulfide linkage which results in the "cys - loop" receptor that is capable of binding acetylcholine and other ligands . These cys - loop receptors are found only in eukaryotes, but prokaryotes possess ACh receptors with similar properties . Not all species use a cholinergic neuromuscular junction; e.g. crayfish and fruit flies have a glutamatergic neuromuscular junction . </P> <P> AChRs at the skeletal neuromuscular junction form heteropentamers composed of two α, one β, one ɛ, and one δ subunits . When a single ACh ligand binds to one of the α subunits of the ACh receptor it induces a conformational change at the interface with the second AChR α subunit . This conformational change results in the increased affinity of the second α subunit for a second ACh ligand . AChRs therefore exhibit a sigmoidal dissociation curve due to this cooperative binding . The presence of the inactive, intermediate receptor structure with a single - bound ligand keeps ACh in the synapse that might otherwise be lost by cholinesterase hydrolysis or diffusion . The persistence of these ACh ligands in the synapse can cause a prolonged post-synaptic response . </P> <P> The development of the neuromuscular junction requires signaling from both the motor neuron's terminal and the muscle cell's central region, During development, muscle cells produce acetylcholine receptors (AChRs) and express them in the central regions in a process called prepatterning . Agrin, a heparin proteoglycan, and MuSK kinase are thought to help stabilize the accumulation of AChR in the central regions of the myocyte . MuSK is a receptor tyrosine kinase--meaning that it induces cellular signaling by binding phosphate molecules to self regions like tyrosines, and to other targets in the cytoplasm . Upon activation by its ligand agrin, MuSK signals via two proteins called "Dok - 7" and "rapsyn", to induce "clustering" of acetylcholine receptors . ACh release by developing motor neurons produces postsynaptic potentials in the muscle cell that positively reinforces the localization and stabilization of the developing neuromuscular junction . </P>

How would antibodies against ach receptors affect the neuromuscular junction