Figure 1.
Bird's eye view of a Kv channel, based on its crystal structure (Long et al., 2007). Each subunit has a different color (red, blue, tan, and yellow), a K+ ion in the selectivity filter is cyan, and the S4 segments of each subunit are black. The VMD program was used for graphics (http://www.ks.uiuc.edu/Research/vmd/).