Electron cryomicroscopy of Bacillus stearothermophilus 50 S ribosomal subunits crystallized on phospholipid monolayers.
50 S ribosomal subunits from Bacillus stearothermophilus have been crystallized as 2-dimensional periodic arrays on phospholipid monolayer films at the water-air interface. These crystals were preserved in vitreous ice and imaged with 100 keV electrons under low dose and low temperature conditions. The unit cell parameters of the crystals are a = 371.3(+/- 3.8) A, b = 152.3(+/- 1.6) A, gamma = 96.3(+/- 1.0) degrees. Some of the image arrays of these crystals have twofold rotational symmetry with a phase residual of less than 25 degrees. The mean figure of merit of the merged structure factors from these image arrays out to 20 A resolution is higher than 0.87. The 2-dimensional projection map shows a level of detail not seen in previous structural studies of the 50 S ribosome subunit. Some of these features may be related to the current 3-dimensional model of the subunit. This analysis illustrates the potential of using the electron crystallographic approach for determining the 3-dimensional structure of the 50 S ribosomal subunit crystallized on a monolayer surface. In addition, the structural information retrieved by electron crystallography might be useful for phasing X-ray data towards an atomic resolution model of the ribosome.
Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX 77030.
A J
AJ
Avila-Sakar
T L
TL
Guan
T
T
Arad
M F
MF
Schmid
T W
TW
Loke
A
A
Yonath
J
J
Piefke
F
F
Franceschi
W
W
Chiu
D003461:Crystallography; D001411:Geobacillus stearothermophilus / Q000737:chemistry*; D007091:Image Processing, Computer-Assisted; D008854:Microscopy, Electron / Q000379:methods; D012270:Ribosomes / Q000737:chemistry* / Q000648:ultrastructure