Three-dimensional structure of (Na+ + K+)-ATPase revealed by electron microscopy of two-dimensional crystals

AbstractProlonged incubation of membrane fragments containing homogeneous (Na+ + K+)-ATPase with Mg2+, K+ and VO3− at 4°C resulted in formation of two-dimensional crystals of this enzyme with unit cell parameters: a = 66 Å, b = 118 Å, γ = 108°. The crystals correspond to the two-sided plane group p21. By combining tilted electron microscopic views of the crystals, a three-dimensional structure of (Na+ + K+)-ATPase was calculated at ~20 Å resolution. The unit cell is formed by two (αβ)-promoters which are in contact in their central parts. The structure was compared with chemical modification and immunochemical data; the arrangement of intra- and extramembrane domains was proposed