Different DNA-binding proteins in the primary and secondary forms of Xenorhabdus luminescens.

Basic, heat-stable proteins binding to double-stranded DNA (HASP) were isolated from the primary and secondary forms of Xenorhabdus luminescens and their composition compared. Two of the proteins with low molecular weight are present in both the primary and secondary forms, whereas two others are present only in the latter. The described protein fractions may be involved in the regulation of transitions between the two forms of X. luminescens.

Proteins of Caulobacter crescentus strongly binding to DNA. Spectroscopic analysis of major histone-like proteins.

The protein composition of deoxyribonucleoprotein (DNP) from Caulobacter crescentus, protected from exogenous nucleases, was analysed. This fraction was obtained by purification of cell lysate on Sephacryl S-400. It contained the following proteins: 13.4 kDa (HCc), 15.2 kDa, 17.5 kDa, 28 kDa and 40 kDa. The strength of protein 15.2 kDa binding to ds-DNA was the same as that of the eukaryotic histones H2A and H2B. Proteins 13.4 kDa (HCc) and 17.5 kDa purified to homogeneity have a UV spectrum identical to protein HU of Escherichia coli which lacks tryptophane and tyrosine. This confirms the classification of protein HCc to the class of HU-like proteins.

Small, heat-stable, DNA-binding proteins from Caulobacter crescentus.

From a heterogenous cell population of Caulobacter crescentus a deoxyribonucleoprotein fraction (DNP) was obtained by the modified technique of Sjåstad et al. (1982). Under the electron microscope DNP had a smooth fibrillar structure. The chemical properties of the proteins associated with the DNA were similar to those of other bacteria. An abundant, heat-stable, basic and DNA-binding protein, termed HCc, which has a molecular weight of 13.4 kD may be an analogue of the HU-histone-like protein from Escherichia coli.

The physiological role of eubacterial histone-like proteins.

This minireview reflects the change in views on the role of histone-like proteins which has occurred in the 1980 s. Initially these proteins were regarded as analogous to eukaryotic histones though distinguished from the latter by much lower strength of binding to DNA. This was attributed to the greater dynamics of the structure of bacterial chromatin. The accumulation in recent years of results testifying to the absence of protein HU in central region of the nucleoid and the participation of this protein in almost all processes involving the recognition of specific DNA sequences by regulatory proteins forces the rejection of the concept of "histone-likeness" and favors the concept of a general, non-specific enhancer of the recognition of sequences acting by causing changes in the secondary structure of a given DNA region.

Isolation and characterization of chromatin from Caulobacter crescentus.

The subunit structure of Caulobacter crescentus chromatin has been proven by electron microscope studies. The use of EDTA-Na2 during the purification of the chromatin complex enhanced the removal of contaminating ribosomes and non-chromatin proteins. The preparation obtained by modified procedure contained RNA polymerase as one of the major proteins and three histone-like proteins (10 K, 17 K and a hitherto not described protein with mol. wt 14 K).