Search PubMed⌕ Search

Biomedical subjects

P Traub

Publications and source records attributed to P Traub.

173 records · Page 10Linked to original sources
PubMed1968

Streptomycin resistance mutation in Escherichia coli: altered ribosomal protein.

Reconstitution of 30S ribosomal particles was performed with 16S ribosomal RNA, "core" proteins, and "split" proteins from 30S particles derived from streptomycin-sensitive and streptomycin-resistant Escherichia coli cells in various combinations. Analysis of streptomycin sensitivity of the reconstituted particles has shown that the alteration induced by the resistance mutation resides in the core proteins, and not in the RNA or in the split proteins of the 30S particles.

Bacterial Proteins↗
PubMedDate not supplied

Cytoskeleton architecture of C6 rat glioma cell subclones differing in intermediate filament protein expression.

Whole-mount electron microscopy was used in conjunction with immunogold labeling to characterize the cytoskeleton architecture of C6 rat glioma cell subclones. These subclones differ in intermediate filament (IF) protein composition and either contain vimentin (subclone C6D8) or do not express any of the known cytoplasmic IF proteins (subclone C6D10) (Röser et al., 1991). In C6D8 cells short thin (3 nm) connecting filaments frequently linked vimentin to actin filaments and, in addition, connected vimentin filaments to each other. Occasionally, direct contacts were noticed between actin and vimentin filaments. Thin connecting filaments were present at a significantly higher number in IF-deficient C6D10 cells, forming a dense cytoplasmic network in conjunction with actin filament bundles as the dominating structure. The data indicate that thin connecting filaments are present in C6 cells independent of the expression of cytoplasmic IF proteins. They suggest that structural linkages between vimentin and actin filaments mediated by thin connecting filaments could play a major role in determining the cytoskeleton architecture of these cells.

Actins↗
PubMedDate not supplied

Polymerizing properties of pepstatin A.

Pepstatin A, a pentapeptide aspartyl protease inhibitor, can spontaneously polymerize into filaments having a helical substructure and, after negative staining, characteristic diameters ranging from 6 to 12 nm. Optical diffraction analysis demonstrated that these filaments consist of a 6-nm-wide strand helically wound with a periodic pitch of 25 nm. Selected images suggest that these filaments may actually be composed of two, intertwined 6-nm-wide strands, an hypothesis not at variance with the diffraction data. These filaments may extend over several micrometers. At low ionic strength and neutral pH, the critical concentration for pepstatin A filament assembly is 0.1 mM. At higher pepstatin A concentrations or in physiological salt solutions, a variety of higher order structures were observed, including ribbons, sheets, and cylinders with both regular and twisted or irregular geometries. Pepstatin A polymerized into these higher order structures loses its ability to inhibit the aspartyl protease of the human immunodeficiency virus type 1. These results have implications not only for model studies on the polymerization of small peptides into higher order structures, but also for the practical development of soluble protease inhibitors.

Microscopy, Electron↗
PubMedDate not supplied

Nucleic acid-binding activities of the intermediate filament subunit proteins desmin and glial fibrillary acidic protein.

In analogy to experimental results previously obtained with vimentin and neurofilament triplet proteins, the intermediate filament (IF) proteins desmin and glial fibrillary acidic protein (GFAP) were also found to have high capacities to associate with nucleic acids. Employing a collection of native and heat-denatured pro- and eukaryotic DNAs, a series of naturally occurring single-stranded (ss)RNAs and a variety of synthetic polynucleotides of the RNA and DNA type, both proteins could be shown to bind preferentially to single-stranded polynucleotides. In the case of ssDNA and synthetic polyribonucleotides, a clear dependency of the binding activity on the G-content of the nucleic acids was demonstrated. The interaction of desmin with ssDNA and tRNA was characterized by strong cooperativity. When a mixture of desmin and vimentin was offered to excess ssDNA, the cooperativity effect brought about segregation of both protein species into two distinct populations of deoxyribonucleoprotein particles with substantially different sedimentation rates; this segregation is in sharp contrast to the ability of desmin and vimentin to form heteropolymers in filament assembly. In general, desmin and GFAP were found to be similar to vimentin and neurofilament proteins in their nucleic acid-binding properties. However, there were also striking differences between individual non-epithelial IF proteins at this level.

Animals↗
PubMedDate not supplied

Interaction in vitro of non-epithelial intermediate filament proteins with histones.

Non-epithelial intermediate filament (IF) subunit proteins show a high and specific affinity for core histones at physiological ionic strength. When IF proteins are titrated with a mixture of core histones and linker histone H1, in general the latter is totally excluded from complexation and in the adducts formed the moderately-arginine-rich histones H2A and H2B are progressively replaced by the very-arginine-rich histones H3 and H4. At histone saturation, 2 molecules of nonneuronal IF protein bind 1 histone H1 molecule or 8 core histone molecules, whereas due to its glutamic acid-rich, C-terminal extensions one dimer of the 68 kD neurofilament protein associates with 3 molecules of histone H1 or 24 molecules of core histones. The salt stability of the insoluble association products is dependent on the amount and arginine content of the constituent histone species. Removal of the non-alpha-helical N- and C-terminal polypeptides from IF proteins by partial chymotryptic digestion does not affect their histone-binding characteristics. Since core histones are only partially inactivated by limited tryptic digestion, they also appear to react through their alpha-helix-rich central domains; the limit peptide derived from histone H1 is completely inactive at physiological ionic strength. Affinity chromatography of rod domains of IF proteins on core histone-Sepharose 4B and of histones and their limit peptides on vimentin-Sepharose 4B has shown that the interactions involving fractions of histones H3 and H4 are extremely resistant to salt and can be dissociated only with arginine or salt under denaturing conditions. In general, the experimental results revealed close parallels between the association of histones with IF proteins and their interaction with DNA.

Animals↗