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Laccases are members of a large family of multicopper oxidases that catalyze the oxidation of a wide range of organic and inorganic substrates accompanied by the reduction of dioxygen to water. A new laccase was isolated from the basidiomycete Coriolopsis caperata strain 0677 and its amino-acid sequence was determined. According to its physicochemical properties and spectroscopic features, the laccase from C. caperata is a high redox-potential blue laccase. Attempts to crystallize the native enzyme were unsuccessful. The copper type 2-depleted (T2D) laccase was prepared and crystallized. The structure of T2D laccase from C. caperata was solved at 1.6 Å resolution, and attempts to reconstruct the T2 copper centre were performed using Cu+ and Cu2+ ions. The structure of T2D+Cu+ laccase was solved at 1.89 Å resolution. It was shown that the T2D+Cu+ laccase structure contained four copper ions in the active site. Reconstruction could not be achieved when the T2D laccase crystals were treated with CuSO4. [ABSTRACT FROM AUTHOR]

Seventy-eight promoter islands with an extraordinarily high density of potential promoters have been recently found in the genome of Escherichia coli. It has been shown that RNA polymerase binds internal promoters of these islands and produces short oligonucleotides, while the synthesis of normal mRNAs is suppressed. This quenching may be biologically relevant, as most islands are associated with foreign genes, which expression may deplete cellular resources. However, a molecular mechanism of silencing with the participation of these promoter-rich regions remains obscure. It has been demonstrated that all islands interact with histone-like protein H-NS - a specific sentinel of foreign genes. In this study, we demonstrated the inhibitory effect of H-NS using Δ hns mutant of Escherichia coli and showed that deletion of dps, encoding another protein of bacterial nucleoid, tended to decrease rather than increase the amount of island-specific transcripts. This observation precluded consideration of promoter islands as sites for targeted heterochromatization only and a computer search for the binding sites of 53 transcription factors (TFs) revealed six proteins, which may specifically regulate their transcriptional output. [ABSTRACT FROM AUTHOR]

Bioactive peptides derived from milk proteins are an active research area. Exhibiting numerous positive physiological effects on digestive, cardiovascular, immune and nervous systems, these peptides thought to be one of the most promising ingredients for functional food. Generally, these peptides are inactive within the parent proteins and can be liberated during milk fermentation by the specific proteolytic systems of various Lactobacillus spp. Here we present the study of milk fermentation by Lactobacillus helveticus NK1, Lactobacillus rhamnosus F and Lactobacillus reuteri LR1 strains. It was demonstrated that the antioxidant activity of the milk fermented by these strains concomitantly increased with the strains' proteolytic activity. For the angiotensin I-converting enzyme (ACE) inhibitory activity, the same tendency was not observed. Although the proteolytic activity of L. helveticus NK1 was two times higher than that of L. rhamnosus F, the milk fermented by these strains showed comparable ACE inhibition. The analysis of the peptide profiles of the fermented milk samples allowed us to hypothesize that some previously unreported peptides can be produced by L. rhamnosus F. In addition, it was demonstrated that these potential ACE-inhibiting peptides originated from the C-terminus of αS2-casein. [ABSTRACT FROM AUTHOR]

Recently, it has been found that bacteria secrete short RNAs able to affect gene expression in eukaryotic cells, while certain mammalian microRNAs shape the gut microbiome altering bacterial transcriptome. The involvement of bacterial RNAs in communication with other bacteria is also expected, but has not been documented yet. Here, we compared the fractions of extremely short (12–22 nucleotides) RNAs secreted by Escherichia coli grown in a pure culture and jointly with bacteria of the Paenibacillus genus. Besides fragments of rRNAs and tRNAs, abundant in all samples, secreted oligonucleotides (exoRNAs) predominantly contained GC-rich fragments of messenger and antisense RNAs processed from regions with stable secondary structures. They differed in composition from oligonucleotides of intracellular fraction, where fragments of small regulatory RNAs were prevalent. Both fractions contained RNAs capable of forming complementary duplexes, while for exoRNA samples a higher percentage of 3΄-end modified RNAs and different endonuclease cleavage were detected. The presence of a cohabiting bacterium altered the spectrum of E. coli exoRNAs, indicating a population-dependent control over their composition. Possible mechanisms of this effect are discussed. [ABSTRACT FROM AUTHOR]