An ancestral MAGUK protein supports the modulation of mammalian voltage-gated Ca channels through a conserved Caβ-like interface.

Eukaryote voltage-gated Ca channels of the Ca2 channel family are hetero-oligomers formed by the pore-forming Caα1 protein assembled with auxiliary Caα2δ and Caβ subunits. Caβ subunits are formed by a Src homology 3 (SH3) domain and a guanylate kinase (GK) domain connected through a HOOK domain. The GK domain binds a conserved cytoplasmic region of the pore-forming Caα1 subunit referred as the "AID".