Heparan sulfate glycosaminoglycans covalently linked to the agrin protein have been shown to play a role in the clustering of AChR. Interference in the correct formation of heparan sulfate through the addition of chlorate to skeletal muscle cell culture results in a decrease in the frequency of spontaneous acetylcholine receptor (AChR) clustering. It may be that rather than solely binding directly to the agrin protein core a number of components of the secondary scaffold may also interact with its heparan sulfate side-chains.