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S Trachtenberg

Publications and source records attributed to S Trachtenberg.

28 records · Page 2Linked to original sources
PubMed1987

Three-dimensional structure of the complex flagellar filament of Rhizobium lupini and its relation to the structure of the plain filament.

Electron micrographs of negatively stained preparations were used to obtain a three-dimensional reconstruction of the complex flagellar filament of Rhizobium lupini H13-3. The complex filament has an organization similar to that of the more common plain filament, but the subunits are perturbed in a pairwise fashion to generate a very distinctive set of three continuous ridges of density along the outer surface of the filament. In the three-dimensional map, the design of the complex filament is similar to that of the plain filament described in the accompanying paper. The structures consist of 11 segmented rods of density lying at a radius of 65 to 70 A. The exterior surfaces of both kinds of filaments consist of features that protrude from the segmented rods. The interiors of both consist of arms that extend inwards from the rods. In the case of the complex filament, but not of the plain filament, the inner arms interact to generate three tubular features, which, together with the three outer ridges, may account for the more brittle and, by implication, stiffer nature of the complex filament.

Computer Simulation↗
PubMed1987

Assemblies of psoriatic keratin and their relation to normal intermediate filament structures.

Protein extracts from normal human epidermis reassemble in vitro into 8-10 nm diameter filaments characteristic of intermediate filaments, whereas extracts from psoriatic epidermal scales reassemble, under identical conditions, into a variety of paracrystalline bundles. Optical diffraction and image analysis of these paracrystalline bundles reveal an axial repeat of 16.5 nm, which subdivides into three bands of 5.5 nm, and a lateral spacing of 5.1 nm. This information, together with available sequence studies of intermediate filaments and biochemical data, suggests that the subunit of psoriatic keratin is made up essentially from the coiled-coil alpha-helical rod domain of the normal keratin subunits, whereas the random coil domains are missing or greatly reduced in size.

Cytoskeleton↗
PubMed1986

Pairwise perturbation of flagellin subunits. The structural basis for the differences between plain and complex bacterial flagellar filaments.

Although plain and complex bacterial flagellar filaments differ in their physical properties and helical symmetry, they both appear to derive from a common underlying structure. Analysis of electron micrographs of complex filaments of Rhizobium lupini revealed that the unit cell has twice the length of that of plain filaments, with a corresponding reduction in helical symmetry whereby the six-start helical family present in plain filaments collapses into a three-start family. Mass per unit length measurements were made by scanning transmission electron microscopy. These, together with the unit cell dimensions and the molecular weight of the flagellin monomer, enabled the number of monomers per unit cell to be estimated. Whereas plain filaments have a single monomer per unit cell, complex filaments have two. These results suggest that complex filament structure differs from plain filament structure by a pairwise perturbation, or interaction, of the flagellin monomers. The additional bonding interactions involved in the perturbation in the complex filament may make it more rigid than the plain filament, which has no such perturbation.

Bacterial Proteins↗
PubMedDate not supplied

The rigidity of bacterial flagellar filaments and its relation to filament polymorphism.

We determined and correlated the rigidity of Salmonella typhimurium, Escherichia coli, and Rhizobium lupini flagellar filaments representing various structural and polymorphic states (plain, complex, straight, superhelical, and right- and left-handed). Persistence length, from which the filament's rigidity and other parameters (Young's modulus, bending force constant, buckling persistence length, flexural deformation, and flexural time) were derived, was determined from electron micrographs of isolated, negatively stained filaments. Outer diameters and radii of strong intersubunit connectivity were determined from three-dimensional image reconstructions and radial mass density profiles from scanning transmission electron microscopy. All filaments appear to be highly rigid with no evident correlation with their helical sense or superhelicity. The complex filament of R. lupini is rigid to the extent that it becomes brittle. The overall flexibility of the flagellum seems to stem mainly from the hook and not from the filament. Polymorphism is probably related to the propelling properties and hydrodynamic shape of the filament rather than to its rigidity.

Escherichia coli↗