Voltage-dependent gating characteristics of the K+ channel KAT1 depend on the N and C termini

We studied how the C and N termini of the plant K+ channel KAT1 influence the voltage-dependent gating behavior by generating C- and N-terminal deletion mutants. Functional expression was observed only when C-terminal deletions were downstream of the putative cyclic nucleotide binding site. Treatments of oocytes expressing KAT1 channels with anticytoskeletal agents indicated that intact microtubules are important for functional expression. C-terminal deletions altered the voltage sensitivity of the KAT1 channel with greater deletions resulting in smaller equivalent charge movements. In contrast, a deletion in the N terminus (delta20-34) shifted the half-activation voltage by approximately -65 mV without markedly affecting the number of equivalent charges. The results reveal novel roles of the N and C termini in regulation of the voltage-dependent gating of KAT1.