Preliminary electron crystallographic analysis of ice-embedded tropomyosin crystals.
Electron images and diffraction patterns of ice-embedded tropomyosin crystalline sheets have been recorded at 100 and 400 kV. Optical diffractograms from the images indicated an elongated, centered unit cell with a = 799.2 +/- 10.6 A, b = 55.1 +/- 3.5 A. Evaluation of the phases in the computed Fourier transforms up to 7 A resolution revealed the presence of symmetry axes consistent with two-dimensional space group cmm. Electron diffraction patterns show diffuse arcs and discrete sampling at a resolution of 5.1 A, arising from the alpha-helical coiled-coil features of the molecule. These results demonstrate that tropomyosin thin sheets are highly ordered and suggest that retrieval of its high-resolution three-dimensional structure may be feasible by electron crystallography.
Avila-Sakar
A J
AJ
Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas 77030.
Schmid
M F
MF
Li
L S
LS
Whitby
F G
FG
Phillips
G N
GN
Chiu
W
W
D000818:Animals; D003461:Crystallography; D004583:Electrons; D007053:Ice; D066298:In Vitro Techniques; D008854:Microscopy, Electron / Q000379:methods; D013552:Swine; D014335:Tropomyosin / Q000648:ultrastructure*
D007053:Ice; D014335:Tropomyosin