Potassium channel Kv1.4 tandem inactivation domain
This family features the tandem inactivation domain found at the N-terminus of the Kv1.4 potassium channel. It is composed of two subdomains. Inactivation domain 1 (ID1, residues 1-38) consists of a flexible N-terminus anchored at a 5-turn helix, and is thought to work by occluding the ion pathway, as is the case with a classical ball domain. Inactivation domain 2 (ID2, residues 40-50) is a 2.5 turn helix with a high proportion of hydrophobic residues that probably serves to attach ID1 to the cytoplasmic face of the channel. In this way, it can promote rapid access of ID1 to the receptor site in the open channel. ID1 and ID2 function together to being about fast inactivation of the Kv1.4 channel, which is important for the channel's role in short-term plasticity.