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.
Sosinsky
G E
GE
Structural Biology Laboratory Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02254.
Francis
N R
NR
Stallmeyer
M J
MJ
DeRosier
D J
DJ
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