Similarity of three-dimensional microcrystals of detergent-solubilized (Na+,K+)-ATPase from pig kidney and Ca(2+)-ATPase from skeletal muscle sarcoplasmic reticulum.
Image analysis has been used to compare the projection structure of three-dimensional crystals of (Na+,K+)-ATPase from pig kidney and the Ca(2+)-ATPase from rabbit muscle sarcoplasmic reticulum. These crystals, formed from detergent-solubilized protein in the presence of 20% glycerol and at a low detergent to protein ratio, crystallize in nearly identical unit cells in the space group C2. Average cell dimensions for the Ca(2+)-ATPase were a = 166.8 +/- 4.5 A, b = 57.7 +/- 4.4 A, gamma = 90 degrees while those for the (Na+,K+)-ATPase were a = 166.2 +/- 3.8A, b = 54.25 +/- 3.5A, gamma = 90 degrees. Their projected structures at the resolution of 25-A resolution are indistinguishable. Thus, the (Na+,K+)-ATPase crystals appear to contain only the alpha chain of the alpha beta heterodimer found in native membranes. We conclude from this that the three-dimensional structure of the alpha chain of the (Na+,K+)-ATPase is very similar to that of the Ca(2+)-ATPase despite their relatively weak overall sequence homology.
Taylor
K A
KA
Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710.
Varga
S
S
D000818:Animals; D000252:Calcium-Transporting ATPases / Q000302:isolation & purification / Q000648:ultrastructure*; D003460:Crystallization; D007668:Kidney / Q000201:enzymology*; D008854:Microscopy, Electron; D008861:Microsomes / Q000201:enzymology*; D009132:Muscles / Q000201:enzymology*; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000302:isolation & purification / Q000648:ultrastructure*; D013552:Swine
D000252:Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase