Electron electrophorus

Figure 30-17 (A) Two-dimensional map of the 260-kDa a subunit of the voltage-gated Na+ channel from the electric eel Electrophorus e/ecfns.438 441 (B) Image of the sodium channel protein obtained by cryo-electron microscopy and image analysis at 1.9 nm resolution. In this side view the protein appears to be bell-shaped with a height of 13.5 nm, a square bottom (cytoplasmic surface) 10 nm on a side, and a hemispherical top with a diameter of 6.5 nm. (C) Bottom view of the protein. (D) Axial section which cuts the bottom, as viewed in (C), approximately along a diagonal. From Sato et al.438 Notice the cavities (dark) and domain structures (light). The black arrow marks a constriction between upper (extracelllar) and lower (cytoplasmic) cavities. White lines indicate approximate position of the lipid bilayer. From Sato et al.i38 Courtesy of Chikara Sato.

In 2001, using cryo-electron microscopy and single particle analysis, Sato and colleagues provided the first three-dimensional view of the Nay channel isolated from the eel Electrophorus electricus. The channel was found to have a bell-shaped extracellular surface structure with square-shaped intracellular base and a spherical top (Figure 16.10). In addition to the pore-forming a-subunits, the Nay channels have four additional accessory subunits (Naypi,-Nayp4), each measuring... 

---