Coevolution of actin and associated proteins: an α-actinin-like protein in a cyanobacterium (Spirulina platensis)

Actin, together with associated proteins, such as myosin, cross-linking or capping proteins, has been observed in all eukaryotic cells. Presence of actin or actin-like proteins has also been reported in prokaryotic organisms belonging to the cyanobacteria. Our aim was first to extend the characterization of an actin-like protein to another prokaryotic cell, i.e. Spirulina, then to compare the antigenic reactivity of this new protein with that of Synechocystis and skeletal actins. We observed that some of the conserved antigenic epitopes corresponded to actin regions known to interact with cross-linking proteins. We also report for the first time that α-actinin and filamin purified from chicken gizzard both interact with a prokaryotic actin-like protein. Finally, we searched for the occurrence of a cross-linking protein in these cyanobacteria and identified a 105-kDa protein as an α-actinin-like protein using specific antibodies.     

Variation of BM224 microsatellite in green frogs of the genus Rana

The variable microsatellite repeat BM224 has been discovered in the genomes of eight species of green frogs (Rana ridibunda, R. cf bedriagae, R. cretensis, R. esculenta, R. lessonae, R. shquiperica, R. saharica, R. nigromaculata). Earlier, this repeat had been observed in members of the genus Bufo. In this paper, a possibility of usage of this genetic marker for species identification is discussed.     

Retroposons of Alu family from <Emphasis Type="Italic">cis</Emphasis>-regulatory modules of <Emphasis Type="Italic">DNAse II</Emphasis> and <Emphasis Type="Italic">CAML</Emphasis> genes affect gene expression in A549 and HEK 293 cells

Promoter fragments of deoxyribonuclease II (DNAse II) and calcium-modulating cyclophilin ligand (CAML) associated with Alu family repeats have been inserted into luciferase reporter vectors. The constructs were introduced into A549 and HEK293 cell lines by transient transfection. Transfected cells were lysed to analyze luciferase activities. It has been shown that Alu repeats inserted into constructs influence the luciferase expression. Therefore, Alu copies associated with cis-regulatory modules in protein-coding genes have biological activity.     

Limited proteolysis of actin by a specific bacterial protease

A 36 kDa fragment of rabbit skeletal muscle actin resistant to further proteolytic breakdown was obtained with a new bacterial protease. This fragment was the only cleavage product obtained from native actin whereas proteolysis of heat-inactivated actin was unlimited. The 36 kDa fragment failed to polymerize and to inhibit DNase I activity. Binding to DNase I protects actin against proteolysis by protease. The results on actin proteolysis by different proteases are compared.     

Structural Similarity between Defense Peptide from Wheat and Scorpion Neurotoxin Permits Rational Functional Design

In this study, we present the spatial structure of the wheat antimicrobial peptide (AMP) Tk-AMP-X2 studied using NMR spectroscopy. This peptide was found to adopt a disulfide-stabilized α-helical hairpin fold and therefore belongs to the α-hairpinin family of plant defense peptides. Based on Tk-AMP-X2 structural similarity to cone snail and scorpion potassium channel blockers, a mutant molecule, Tk-hefu, was engineered by incorporating the functionally important residues from κ-hefutoxin 1 onto the Tk-AMP-X2 scaffold. The designed peptide contained the so-called essential dyad of amino acid residues significant for channel-blocking activity. Electrophysiological studies showed that although the parent peptide Tk-AMP-X2 did not present any activity against potassium channels, Tk-hefu blocked Kv1.3 channels with similar potency (IC₅₀ ∼ 35 μm) to κ-hefutoxin 1 (IC₅₀ ∼ 40 μm). We conclude that α-hairpinins are attractive in their simplicity as structural templates, which may be used for functional engineering and drug design.     

Retroposons of Alu family from cis-regulatory modules of DNAse II and CAML genes effect gene expression in A549 and HEK293 cells

Different fragments of promoters of deoxyribonuclease II (DNAse II) and calcium-modulating cyclophilin ligand (CAML) associated with Alu family repeats have been inserted into a luciferase reporter vector. These constructions were introduced into A549 and HEK293 cell lines and after transient transfection we lysed cells and analysed luciferase activities in these lysates. It has been shown that Alu repeats localized in constructions influence expression of luciferase. Therefore, Alu copies which are associated with cis-regulatory modules of protein-coding genes have biological activity.     

SINEs in mammalian genomes can serve as additional signals in formation of facultative heterochromatin

Using computer-based methods, we determined the global distribution of short interspersed nuclear elements (SINEs) on human and mouse X chromosomes. It was shown that this distribution was similar to the distribution of CpG islands and genes, but was different from the distribution of LINE1 elements. Since SINEs (human Alu and mouse B2) may have binding sites for Polycomb protein YY1, we suggest that these repeats can serve as additional signals (“boosters”) in Polycomb-dependent silencing of gene-rich segments during X inactivation.