Substructure of the flagellar basal body of Salmonella typhimurium.
The Salmonella typhimurium basal body, a part of the flagellar rotary motor, consists of four rings (denoted M, S, P and L) and a coaxial rod. Using low-dose electron microscopy and image averaging methods on negatively stained and frozen-hydrated preparations, we examined whole basal body complexes and subcomplexes obtained by dissociation in acid. Dissociation occurs in steps, allowing us to obtain images of substructures lacking the M ring, lacking the M and S rings, and lacking the M and S rings and the proximal portion of the rod. We obtained images of the L and P ring subcomplex. The existence of a subcomplex missing only the M ring suggests either that the S and M rings derive from two different proteins, or that the M ring is a labile domain of a single protein, which makes up both rings. At the 25 to 30 A resolution of our averaged images, the L, P and S rings appear cylindrically symmetric. Images of the M ring show variability that may be due to differences in angular orientation of the grid, but equally could be due to structural variations. Three-dimensional reconstructions of these structures from the averaged images reveal the internal structure and spatial organization of these components.
Structural Biology Laboratory Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02254.
G E
GE
Sosinsky
N R
NR
Francis
M J
MJ
Stallmeyer
D J
DJ
DeRosier
D005407:Flagella / Q000648:ultrastructure; D005615:Freezing; D006863:Hydrogen-Ion Concentration; D007091:Image Processing, Computer-Assisted; D046911:Macromolecular Substances; D012486:Salmonella typhimurium / Q000648:ultrastructure*; D013194:Staining and Labeling
D046911:Macromolecular Substances