Properties of Escherichia coli deoxyribonucleoprotein as compared with the deoxyribonucleoprotein of higher organisms

Differences in pattern of a DNA protein complex isolated from vegetative cells and spores of Bacillus subtilis

A DNA protein complex has been isolated from vegetative cells and spores of Bacillus subtilis. Properties of the DNA protein complex prepared from vegetative cells were studied and SDS gel electrophoresis was employed to compare the different DNase-untreated and -treated DNA protein complexes. It is concluded that proteins are associated with the DNA and differences in protein pattern in polyacrylamide gels indicates the involvement of DNA-binding proteins in the regulation of spore formation.

Visualization of prokaryotic DNA in a regularly condensed chromatin-like fiber

Electron microscopy of disrupted Escherichia coli cells under certain conditions revealed loops of a fiber 120 A in diameter which were attached to the cell envelope and showed a 130 A repeating beaded substructure. These fibers were detected only when the cells were lysed in 0.15 M NaCl solutions directly on the electron microscope supporting films and if the dehydration steps began within 2 min of lysis. Under these conditions examination of cells lysogenic for phage lambda after superinfection with lambda wild type or deletion mutants disclosed short loops of a 120 A diameter fiber free of the cell envelope. Because the contour length of these loops was proportionate to the DNA content of the superinfecting lambda phage, it was concluded that the fibers contained DNA condensed 6.5-fold in blocks of about 250 base pairs.

Apparent thermal destabilization of Escherichia coli nucleoprotein due to the incomplete dialysis of EDTA

Escherichia coli nucleoprotein has been found to undergo thermal denaturation approx. 5 degrees C lower than purified E. coli DNA, measured in 0.25 mM sodium EDTA, pH 8.0 (Searcy, D.G. (1975) Biochim. Biophys. Acta 395, 535-547). This is now shown to be an artifact due to the impermeability of dialysis membranes to sodium EDTA, especially at low concentrations such as 1 mM or less. Thermal denaturation data can be corrected by measuring the electrical conductivity of the solutions. When this is done, the nucleoprotein and DNA both denature at the same temperature.

Histone-like protein in the prokaryote Thermoplasma acidophilum

The DNA of the prokaryote Thermoplasma acidophilum is associated with a histone-like protein that has the following properties: it has a high content (23%) of basic amino acids, is positively charged at neutral pH, is soluble in acid, and can stabilize DNA against thermal denaturation. In polyacrylamide gel electrophoresis, in the presence of either sodium dodecylsulfate or urea, it migrates at the same rate as histone IV (F2a1) of calf thymus. The amino acid composition, however, it unusually rich in the amides of acidic amino acids (16-20%), and it does not appear to be closely homologous to any of the classes of eukaryotic histones. Escherichia coli DNA, on the other hand, was associated with no detectable acid-soluble proteins, and the nucleoprotein thermally denatured at a lower temperature than pure DNA.

A kinetic study of DNA and basic protein metabolism during spermatogenesis in the sand crab, Emerita analoga

Cytochemical and radioautographic techniques define and confirm a staging scheme for developing spermatids of the decapod crab, Emerita analoga. Quantitative photometric data demonstrate that developing spermatids lose a significant proportion of their nuclear proteins, as evidenced by diminishing binding of fluorodinitrobenzene. Photometric results also show that much (but not all) of the spermatid nuclear protein loss is in somatic-type histone, as evidenced by a dramatic fall in the histone/DNA ratio of these cells during a period in which nuclear DNA content remains constant. By the end of spermiogenesis, the sperm nuclear histone and protamine content is approximately zero, whereas some nonbasic protein persists. Loss of spermatid nuclear somatic-type histone is not accompanied by synthesis of gamete-type histone (e.g. protamine or arginine-rich histone), showing that the processes of displacement and synthesis of nuclear basic proteins during histone transition are not subject to obligatory coupling. Labeling studies suggest that nonbasic acrosomal proteins (presumably partly enzymes) are synthesized in the cytoplasm, after which they move into the acrosome. Stainable basic proteins accumulate in the acrosome during precisely the period of nuclear somatic histone loss, suggesting nuclear-cytoplasmic transfer.