α1-β interaction in voltage-gated cardiac L-type calcium channels

The β subunits of voltage-gated calcium channels normalize current amplitude, kinetics and voltage dependence of these channels by interacting with the channel's pore forming subunit α1. By screening an epitope expression library of α1Ca fusion proteins, a β2a binding site of 22 amino acids was identified within the I–II cytoplasmic linker but not on other cytoplasmic sequences of α1Ca. This binding site overlaps by 14 amino acids with the conserved 18 amino acid peptide assumed to be essential for α1-β interaction. The common 14 amino acid motif of α1Ca is sufficient to bind β2a, and in addition β1a, β3 and β4.