Computer image analysis of two-dimensional crystals of beef heart NADH: ubiquinone oxidoreductase fragments. II. Comparison of frozen hydrated and negatively stained specimens.
Two-dimensional crystals of bovine NADH: ubiquinone oxidoreductase fragments were studied by cryo-electron microscopy and computer image analysis at two focus settings. The lattice parameters of the crystals were determined as a = 14.5 +/- 0.2 nm, b = 14.8 +/- 0.3 nm with gamma = 87.8 degrees +/- 0.2 degrees. Translation and rotation alignment resulted in a final resolution of 1.38 (close-to-focus) or 1.9 nm (1.3 microns underfocus). When only translational alignment was employed 1.6 nm resolution resulted (close-to-focus case). The application of a further correction procedure surprisingly lowered the achieved resolution to 2.2 nm. A combination of the projected structures for the two focus settings in Fourier space resulted in a noise-free image displaying enhanced image contrast for reciprocal spacings from 1/5.0 to 1/1.4 nm-1. The structure in amorphous ice comprises four separate quasi-identical motifs, each resembling a distorted triangle. Two symmetry-related (p2) motifs reveal a pore-like feature. In negative stain the structure has p4mm symmetry. The absence of in-plane symmetry elements (i.e. twofold rotation and screw axes) and other differences might be accounted for (at least in part) if the crystal studied was slightly tilted.
Brink
J
J
Biochemisch Laboratorium, Rijksuniversiteit Groningen, The Netherlands.
Booy
F P
FP
Van Bruggen
E F
EF
D000818:Animals; D002417:Cattle; D003460:Crystallization; D005615:Freezing; D007091:Image Processing, Computer-Assisted; D008854:Microscopy, Electron / Q000379:methods*; D009206:Myocardium / Q000201:enzymology; D016660:NAD(P)H Dehydrogenase (Quinone); D011808:Quinone Reductases / Q000032:analysis*; D013194:Staining and Labeling
D016660:NAD(P)H Dehydrogenase (Quinone); D011808:Quinone Reductases