Substructure of the flagellar basal body of Salmonella typhimurium

Sosinsky, Gina E.; Francis, Noreen R.; Stallmeyer, M.J.B.; DeRosier, David J.

doi:10.1016/0022-2836(92)90724-x

Cited by 36 publications

(28 citation statements)

References 18 publications

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“…Our previous experience with alignment of the coaxial rings of the flagellar motor (17,18) suggested that conformational variability due to flexing of the structure was a source of distortion in our averaged images. For the motor, we improved the average of a particular component by using that component alone for the alignment.…”

Section: Resultsmentioning

confidence: 99%

Three-dimensional structure and organization of a receptor/signaling complex

Francis

Wolanin

Stock

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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Transmembrane signaling in bacterial chemotaxis has become an important model system for experimental and theoretical studies. These studies have provided a wealth of detailed molecular structures, including the structures of CheA, CheW, and the cytoplasmic domain of the serine receptor Tsr. How these three proteins interact to form the receptor͞signaling complex remains unknown. By using EM and single-particle image analysis, we present a three-dimensional reconstruction of the receptor͞signaling complex. The complex contains CheA, CheW, and the cytoplasmic portion of the aspartate receptor Tar. We observe density consistent with a structure containing 24 aspartate-receptor monomers and additional density sufficient to house the expected four CheA monomers and six CheW monomers. Within this bipolar structure are four groups of three receptor dimers that are not threefold symmetric and are therefore unlike the symmetric trimers observed in the x-ray crystal structure of the cytoplasmic domain of the serine receptor. In the latter, the interdimer contacts occur in the signaling domains near the hairpin loop. In our structure, the signaling domains within trimers appear spaced apart by the presence of CheA and CheW. This structure argues against models where one CheA and one CheW bind to the outer face of each of the dimers in the trimer. This structure of the receptor͞signaling complex provides an additional basis for understanding the architecture of the large arrays of chemotaxis receptors, CheA, and CheW found at the cell poles in motile bacteria.chemotaxis ͉ electron microscopy ͉ macromolecular assembly ͉ signal transduction M otile bacteria are capable of detecting and moving in response to gradients of nutrients, oxygen, light, and other stimuli. They do so in response to temporal changes in the stimuli by altering the behavior of the motors that generate the force for cell movement. The signal transduction system controlling bacterial chemotaxis has become an important model for the study of transmembrane signaling, and the most studied system is that in Escherichia coli.The core components of the E. coli chemotaxis signaltransduction system are found in nearly all motile bacteria and consist of transmembrane chemoreceptors; an associated histidine kinase, CheA; and an associated CheA-activator, CheW. Signaling occurs within the context of the assembled receptor͞ CheW͞CheA complexes within a large, densely packed patch of chemoreceptors, which is typically located at one (or both) poles of the cell (1). No gross structural changes in the receptor͞ signaling complex are observed in response to stimulatory ligands (2).Recent studies and modeling of the chemotaxis system have emphasized the importance of interactions among large numbers of receptors in terms of the system's sensitivity and adaptive response (3, 4), and chemoreceptors for different ligands appear to communicate with one another (3). The lack of detailed information about how CheA and CheW interact with the chemoreceptors and each other in the ...

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Section: Resultsmentioning

confidence: 99%

Three-dimensional structure and organization of a receptor/signaling complex

Francis

Wolanin

Stock

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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“…The images were then masked from their surroundings so that all images had the same dimensions. Separate averages were produced based on alignment of the L and P rings, the M and S rings, and the C rings, and these separate averages were spliced into a single image (16). The reason for averaging parts separately is that the images of the basal bodies are not quite superposable so that alignment and averaging of the parts produced sharper features than alignment of the whole structure.…”

Section: Methodsmentioning

confidence: 99%

Structures of Bacterial Flagellar Motors from Two FliF-FliG Gene Fusion Mutants

2001

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“…4 nm (23), must be penetrated by the rod, which has a diameter of ca. 11 nm (33). FlgJ, which is required for rod assembly (19) in beta-and gammaproteobacteria, has a dual function: acting as a scaffold for rod assembly and also acting as a muramidase degrading the PG layer to facilitate rod penetration (13,27).…”

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confidence: 99%