1.A.1.12.2
Acanthocystis turfacea chlorella virus cation, K⁺-preferring, channel, ATCV1 (82aas and 2 TMSs) (Gazzarrini et al., 2009; Siotto et al. 2014). The difference in open probability between close isoforms is caused by one long closed state in Kcv_S versus Kcv_NTS. This state is structurally created in the tetrameric channel by a transient, Ser mediated, intrahelical hydrogen bond. The resulting kink in the inner transmembrane domain swings the aromatic rings from downstream Phenylalanines in the cavity of the channel, which blocks ion flux. The most conserved region of the Kcv protein is the filter, the turret and the pore helix, and the outer and the inner transmembrane domains of the protein are the most variable (Murry et al. 2020).