Novel histone H2A-like protein of escherichia coli.

Abstract

ABSIRACT A histone-like protein (H) from Escherichia coli has been purified to more than 98% homogeneity by using its capacity to inhibit DNA functions. H protein behaves as a dimer of 28,000-dalton subunits. The histone H2A-like properties of H protein are: (i) The Escherichia coli chromosome can be isolated in a folded, condensed, supercoiled form (1-4). A search for histone-like proteins in E. coli and other prokaryotes has yielded several low molecular weight, basic, DNA-binding proteins that resemble eukaryotic histones (5)(6)(7)(8)(9). A pair of HU proteins, also known as protein 2, are near 9000 daltons in size and resemble the eukaryotic histones in (i) binding to DNA, (ii) having an amino acid composition like that of histone H2B, (ii) being heat and acid stable, and (iv) forming a nucleosome-like structure with duplex DNA (9, 10). In addition, a histone-like protein of 17,000 daltons in E. colh (8) and a low molecular weight protein in thermophilic mycoplasma (Thermoplasma acidophilum) similar to histone H4 (11) have been described.In the course of purifying E. colh replication proteins (12) and possible regulatory factors, we encountered an inhibitor that appears to be a novel histone-like protein, provisionally called H protein, that shows immunological crossreactivity with the eukaryotic histone H2A. As a result of tight binding to DNA, H protein inhibits DNA functioning as a template for polymerases, as a substrate for nuclease and topoisomerase, and as an effector for ATPase; it also activates annealing of homologous single strands. H protein may have a significant role in the structure and function of the E. coli chromosome. MATERIALS AND METHODSNucleic Acids, Nucleotides, Enzymes, and Proteins. kX174and M13 DNA were prepared as described (13) sl of 50 mM NaOAc, pH 4.6/150 mM NaCl/1 mM Zn(OAc)2 was added, followed by 100 units of S1 nuclease. Incubation was at 370C for 30 min. After addition of calf thymus ss DNA to 150 ,ug/ml and precipitation with an equal volume of 10% (wt/vol) trichloroacetic acid, the acid-insoluble radioactive material was filtered and measured as described (15). Under these conditions, in the absence of H protein, 3% of the input DNA was acid insoluble (S1 nuclease resistant). The acid-insoluble radioactivity of native P22 [3H]DNA was taken as the 100% S1 nucleasbresistant value.Antisera and Enzyme-Linked Immunosorbent Assay (ELISA). Antisera against calf thymus histones HI, H2A, and H2B were prepared in rabbits by R. Sperling and M: Bustin as described (17), and their specificity was measured by complement fixation (18).

A procaryotic regulatory factor with a histone H1-like carboxy-terminal domain: clonal variation of repeats within algP, a gene involved in regulation of mucoidy in Pseudomonas aeruginosa

“…Since algR belongs to a large group of regulatory elements in bacteria sharing similar mechanisms of activation (11) from P. aeruginosa (61). These proteins are termed histonelike proteins on the basis of their amino acid composition similarity to histones H2A and H2B, their abundance, and their tight association with the chromosomal DNA (30,53). However, these basic bacterial histonelike proteins do not show sequence (primary structure) similarity to eucaryotic histones and display several functional and structural differences in their binding to DNA (17,61).…”

Visualization of a Spinach Plastid Transcriptionally Active DNA-Protein Complex in a Highly Condensed Structure

“…The presence of prokaryotic histone-like proteins is now well documented for E. coli since Rouviere-Yaniv and Gros (17) 10-. appear to be organized in a condensed form in chromatin in prokaryotic chromosomes, and, as we show, in plastome of higher plants. Basic proteins could play an essential function in the condensed form of plastid DNA as they do in E. coli (13,17) and in nuclear chromatin.…”

Introduction of proteins into living bacterial cells: distribution of labeled HU protein in Escherichia coli

“…However, early studies of purified ribosomes led to the conclusion that HU (also called protein NS) was associated with 30S ribosomes (30). This uncertainty about HU was raised with the finding that protein H, which at one time was thought to be a major nucleoid-associated histonelike protein (12), is ribosomal protein S3 (3). The investigators proposed that other histonelike proteins may likewise be ribosomal proteins.…”