Transmembrane segments critical for potassium channel function.

The relative contribution of the transmembrane segments in the alpha-subunit of Shaker-type potassium channels was investigated in relation to potassium channel function. Starting from a wild-type Kv1.1 channel, four different deletion mutants were made, missing respectively transmembrane segments S1 and S2, S2 and S3, S1 to S3, and S1 to S4. To ensure the assembly of the different subunits, the hydrophylic N-terminal domain was always conserved. The lack of transmembrane segments S1 to S4 converts a depolarization-activated WT Kv1.1 channel with outward rectification into a hyperpolarization-activated channel with inward rectification. In contrast, mutant channels missing transmembrane segments S1 and S2, S2 and S3, or S1 to S3 did not reveal functional expression.