Caskin proteins are multidomain adaptor proteins that contain six ankyrin repeats, a single SH3 domain, tandem sterile alpha motif (SAM) domains, and a long disordered proline-rich region. There are two Caskin proteins called Caskin1 and Caskin2. Caskin1 binds to the multidomain scaffolding protein CASK through the CaM domain in competition with Munc-interacting protein 1 (Mint1). CASK participates in one of two evolutionarily conserved tripartite complexes containing either Mint1 and Velis or Caskin1 and Velis. Caskin1 may play a role in infantile myoclonic epilepsy. There is not much known about Caskin2; despite sharing a domain architecture with Caskin1, Caskin2 does not bind CASK. SH3 domains bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs; they play a role in the regulation of enzymes by intramolecular interactions, changing the subcellular localization of signal pathway components and mediate multiprotein complex assemblies.
Jiyao W et al.(2023). "The conserved domain database in 2023.",