CASK (Calcium/calmodulin-dependent serine protein kinase) a multidomain synaptic scafolding protein binds to the extreme C terminus of neurexins (Hata et al. 1996). In brain, CASK binds to MINT1 with its CaM kinase domain, and all three Velis with the region between the CaM kinase and PDZ domains to form a tight tripartite complex (Butz et al. 1998). This tripartite complex may serve as nucleation site for the assembly of synaptic plasma membrane proteins. Recruitment of this tripartite complex to the plasma membrane by binding to neurexins may be involved in synaptic vesicle traffic.