Caspr is a contactin-associated protein. Caspr is part of the neurexin family of proteins. Caspr is a membrane protein found in the neuronal membrane in the paranodal section of the axon in myelinated neurons, between the Nodes of Ranvier containing Na+ channels, and juxtaparanode, which contains K+ channels. During myelination, caspr associates with contactin in a cis complex, though its precise role in myelination is not yet understood.
In Western Blotting it has a predicted Molecular Weight around 156kDa but due to a number of potential glycosylation sites, is 180kDa.
References
Caspr Wikipedia(Text) CC BY-SA