Endolysin of bacteriophage T5 (EndoT5) is a Zn2+-dependent and Ca2+-activated L-alanyl-D-glutamate peptidase that hydrolyses peptidoglycans during the destruction of the cell wall of the phage host bacterium Escherichia coli. To elucidate the mechanism of calcium activation, the spatial solution structure of EndoT5 in a complex with two ions - catalytic Zn2+ and regulatory Ca2+ (EndoT5-Zn2+Ca2+, PDB ID: 8P3A) was determined by high-resolution NMR and deposited in the Protein Data Bank. We show that coordination of the Ca2+ ion fix the spatial position of polar amino acid residues D113, N115 and S117. As a result, the intramolecular mobility of extended protein loops (residues 40-70 and 111-132) is significantly reduced compared to the mobility of these loops in the structure of an enzyme containing only a catalytic a Zn2+ ion (EndoT5-Zn2+, PDB ID: 2MXZ). In the stabilized EF-like calcium-binding loop (residues 111-132), the number of van der Waals interactions with amino acid residues of the globular core of the protein increases. The binding of the Ca2+ ion is accompanied by the selection of the functional states of both extended loops of the enzyme (residues 40-70 and 111-132), because of which EndoT5-Zn2+Ca2+ acquires the structural integrity necessary for catalysis. Therefore, the mechanism of activation of L-alanyl-D-glutamate peptidase of bacteriophage T5 by Ca2+ ions involves stabilization of the enzyme molecule in a catalytically active “open” conformation. This work sheds light on the structural grounds of the ion-dependent functional proteoforms of this interesting protein.

The inert gas xenon (Xe) is increasingly used in medicine as a universal anesthetic, a regulator of cellular metabolism, and a broad-spectrum organoprotector. Commonly utilized Xe inhalation requires expensive equipment that is not universally available. Here we describe the production process and physical characteristics of a solid, highly stable xenon carrier based on α-cyclodextrin (α-CD), developed for oral administration. It was found, that the interaction of α-CD with Xe in an aqueous solution and elevated pressure leads to precipitation of the α-CD-Xe complex. We have discovered three new properties of the resulting complex that promote long-term storage and oral delivery of Xe. (i) At temperatures below 0 °C, the precipitated α-CD-Xe complex containing water is so stable that it allows the removal of water by vacuum freeze-drying (lyophilization). (ii). Lyophilized α-CD-Xe remains stable for months at room temperature. (iii) Upon contact with water, α-CD-Xe rapidly releases gaseous Xe. As revealed in the forced swim test, after oral administration of lyophilized α-CD-Xe to rats, the duration of swimming was significantly increased. The obtained data open up prospects for the development of drugs based on the lyophilized α-CD-Xe complex suitable for storage, transportation, and medical use, including outside the hospital.

Background Endolysins of a number of bacteriophages, including coliphages T5, RB43, and RB49, target the peptidoglycans of the bacterial cell wall. The backbone of these bacterial peptidoglycans consist of alternating N-acetylglucosamine and N-acetylmuramic acid residues that is further “reinforced” by the peptide subunits. Because of the mesh-like structure and insolubility of peptidoglycans, the processes of the peptidoglycan binding and hydrolysis by enzymes cannot be studied by spectral methods. To overcome these issues we synthesized and analyzed here one of the simplest water soluble peptidoglycan mimetics. Methods A compound has been synthesized that mimics the peptidoglycan fragment of the bacterial cell wall, N-acetylglucosaminyl-β(1-4)-N-acetylmuramoyl-l-alanyl-γ-d-glutamyl-l-alanyl-d-alanine. NMR was used to study the degradation of this peptidoglycan mimetic by lytic l-alanoyl-d-glutamate peptidases of colibacteriophages T5, RB43, and RB49 (EndoT5, EndoRB43, and EndoRB49, respectively). Results The resulting glycopeptide mimetic was shown to interact with the studied enzymes. Its hydrolysis occurred through the bond between l-Ala and d-Glu. This artificial substrate mimetic was hydrolyzed by enzymes at different rates, which decreased outside the pH optimum. The EndoT5 demonstrated the lowest hydrolysis rate, whereas the EndoRB49-driven hydrolysis was the fastest one, and EndoRB43 displayed an intermediate potency. These observations are consistent with the hypothesis that EndoRB49 is characterized by the lowest selectivity, and hence the potentially broader spectrum of the peptidoglycan types subjected to hydrolysis, which was put forward in the previous study. We also show that to hydrolyze this glycopeptide mimetic, enzymes approach the glycopeptide near the methyl groups of all three alanines.

The methods of solution NMR, circular dichroism (CD), and differential scanning calorimetry (DSC) were used to study two zinc-containing L-alanyl-D-glutamate peptidases - endolysins of the pseudo T-even myoviruses RB43 and RB49 (EndoRB43 and EndoRB49, respectively), which are orthologous to the EndoT5, which is a zinc-containing L-alanyl-D-glutamate peptidase of the T5 siphovirus. The spatial conservation of the Zn2+-binding sites for the enzymes EndoT5, EndoRB43, and EndoRB49 was established, and the key role of Zn2+ ions in the stabilization of the spatial structures of these three peptidases was confirmed. We are showing here that the binding of the Zn2+ ion in the active center of EndoRB49 peptidase causes conformational rearrangements similar to those observed in the EndoT5 peptidase upon binding of Zn2+ and Ca2+ ions and lead to the formation of a catalytically active form of the enzyme. Therefore, the binding of the Zn2+ ion to the active site of EndoRB49 peptidase is a necessary and sufficient condition for functioning of this protein.

Structural consequences of the binding of metal ions (regulatory Ca2+ and catalytic Zn2+) to the metalloenzyme l-alanyl-d-glutamate peptidase of the bacteriophage T5 (Endo T5) and some of its analogues containing single amino acid substitutions in the active center were analyzed by nuclear magnetic resonance (NMR), circular dichroism (CD) and calorimetry. Analyses revealed that the native EndoT5 undergoes strong structural rearrangements as a result of Zn2+ binding. This structural rearrangement resulting in the formation of an active enzyme is completed by the Ca2+ binding. In this case, the NMR spectra uncover the tautomerism of the NH protons of histidine imidazoles responsible for the Zn2+ coordination. For the EndoT5 analogues with point substitutions in the Ca2+-binding site, similar conformational rearrangements are observed upon Zn2+ binding. However, no characteristic changes in the NMR spectra associated with the Ca2+ binding were detected. The roles of the proton exchange in the process of Ca2+-induced activation of the enzymatic activity of EndoT5 is discussed.

Communicated by Ramaswamy H. Sarma.

Peptidoglycan hydrolase of bacteriophage T5 (EndoT5) is a Ca2+-dependent l-alanyl-d-glutamate peptidase, although the mode of Ca2+ binding and its physiological significance remain obscure. Site-directed mutagenesis was used to elucidate the role of the polar amino acids of the mobile loop of EndoT5 (111-130) in Ca2+ binding. The mutant proteins were purified to electrophoretic homogeneity, the overall structures were characterized by circular dichroism, and the calcium dissociation constants were determined via NMR spectroscopy. The data suggest that polar amino acids D113, N115, and S117 of EndoT5 are involved in the coordination of calcium ions by forming the core of the EF-like Ca2+-binding loop while the charged residues D122 and E123 of EndoT5 contribute to maintaining the loop net charge density. The results suggest that Ca2+ binding to the EndoT5 molecule could be essential for the stabilization of the long mobile loop in the catalytically active "open" conformation. The possible mechanism of Ca2+ regulation of EndoT5 activity during bacteriophage T5's life cycle through the Ca2+ concentration difference between the cytoplasm and the periplasm of the host bacteria cell has been discussed. The study reveals valuable insight into the role of calcium in the regulation of phage-induced bacterial lysis.

Aims: To initiate a state of artificial torpor we suggested a pharmacological multi-targeting strategy for simulation of the physiological pattern of natural hibernation including a significant reduction in heart rate, respiratory rate, body temperature and oxygen consumption as well as a decline in brain activity known as torpor. Materials and methods: We have developed a composition which initiates a pharmacologically induced torporlike state (PITS-composition), made up of eight therapeutic agents, inert gas xenon and lipid emulsion served as a drug vehicle. Key findings: After a single intravenous injection to rats, PITS-composition causes a rapid decline in heart rate followed by a steady decrease in body temperature from about 38.5 degrees C to 31.5 degrees C, at ambient temperature of 22 degrees C-23 degrees C. The hypothermic state may continue on average for 16-17 h with the subsequent spontaneous return of heart rate and body temperature to the initial values. In the open field test at torpor the motility, rearing and grooming were suppressed but 4-8 days later they were restored. Significance: Suspended animation states, including natural hibernation or pharmacologically induced synthetic torpor are of special attention of medicine, since it may improve survival rate after cardiac arrest, brain hemorrhage and ischemia, and during long-term space traveling. The suggested here multi-targeting strategy made possible to develop the pharmacological composition able, after a single intravenous injection, to initiate long, stable and reversible hypothermia and torpor at room temperature. After the torpor, animals were able to spontaneously restore both physiological parameters, and behavioral reactions.

In this work, we studied the effect of the C-terminally attached poly-histidine tag (His-tag), as well as the peculiarities of the protein purification procedure by the immobilized metal affinity chromatography (IMAC) on the activity and structure of the metalloenzyme, l-alanyl-d-glutamate peptidase of bacteriophage T5 (EndoT5), whose zinc binding site and catalytic aspartate are located near the C-terminus. By itself, His-tag did not have a significant effect on either activity or folding of the polypeptide chain, nor on the binding of zinc and calcium ions to the protein. However, the His-tagged EndoT5 samples had low shelf-life, with storage of these samples resulting in an increased propensity for protein self-association and decreased enzymatic activity of EndoT5. Furthermore, disastrous effects on the activity of the enzyme were exerted by the presence of imidazole and nickel ions accompanying metal chelate chromatography. The activity of the protein can be restored by thorough washing off of these low molecular impurities via the prolonged dialysis of the His-tagged EndoT5 samples at the specifically elaborated conditions.

Abstract—A study of redox reaction kinetics in chromium-containing fixatives (mixtures of chromic acid, bichromate, formaldehyde, and acetic acid) showed that these fixatives were unstable chemical mixtures characterized by rapid kinetics of redox processes. Therefore, biological material fixation occurs in a non-stationary solution of a variable composition, including chromic acid, bichromates (chromium(VI)), formaldehyde, acetic acid, formic acid, and chromium(III) acetate. We propose the division of chemical fixation in these fixatives into two successive stages (“two-step fixation protocol”): the tissue is fixed in an acetic acid–formaldehyde mixture (a rapidly penetrating fixing mixture) at the first stage and washed thoroughly, and treated by the mordant for the staining at the second stage. Such a protocol will at least preserve the original composition of chromium-containing fixatives.

It is known that some metals (Cu, Zn, Cd, Au) markedly increase the toxic effect of thiocarbamates. It was shown in the present study that hydroxycobalamin (a form of vitamin B-12, HOCbl), which incorporates cobalt, significantly enhances the cytotoxicity of diethyldithiocarbamate (DDC), decreasing its IC50 value in tumor cells three to five times. The addition of HOCbl to aqueous DDC solutions accelerated the reduction of oxygen. No hydrogen peroxide accumulation was observed in DDC + HOCbl solutions; however, catalase slowed down the oxygen reduction rate. Catalase as well as the antioxidants N-acetylcysteine (NAC) and glutathione (GSH) partially inhibited the cytotoxic effect of DDC + HOCbl, whereas ascorbate, pyruvate, and tiron, a scavenger of superoxide anion, had no cytoprotective effect. The administration of HOCbl into DDC solutions (> 1 mM) resulted in the formation of a crystalline precipitate, which was inhibited in the presence of GSH. The data of UV and NMR spectroscopy and HPLC and Mass Spectrometry (LC/MS) indicated that the main products of the reaction of DDC with HOCbl are disulfiram (DSF) and its oxidized forms, sulfones and sulfoxides. The increase in the cytotoxicity of DDC combined with HOCbl occurred both in the presence of Cu2+ in culture medium and in nominally Cu-free solutions, as well as in growth medium containing the copper chelator bathocuproine disulfonate (BCS). The results indicate that HOCbl accelerates the oxidation of DDC with the formation of DSF and its oxidized forms. Presumably, the main cause of the synergistic increase in the toxic effect of DDC + HOCbl is the formation of sulfones and sulfoxides of DSF.

Using high-resolution NMR spectroscopy, we studied peculiarities of the unfolding process of the bacteriophage T5 endolysin (EndoT5) by strong denaturants. It was shown that in the absence of zinc ions this protein is mostly unfolded in the solution of 8 M urea or 6 M guanidine hydrochloride. However, in the presence of zinc ions EndoT5 unfolding can be achieved only in acidic solutions (at pH < 4.0), whereas at pH > 4.0 NMR spectra of the metal-bound protein (Zn2+–Ca2+–EndoT5 or Zn2+–EndoT5 complexes) exhibit a few chemical shifts characteristic of the native or native-like proteins. Our data, including the pH–titration curve with the pK of ~5, suggested involvement of the zinc-binding histidines in the stabilization of this protein. Up-field signals that appear in the NMR spectra of apo-EndoT5 in the presence of high concentrations of strong denaturants are probably derived from the amino acid residues included in the formation of structured hydrophobic cluster, which likely corresponds to the 81–93 region of EndoT5 and contains some residual tertiary structure. It is possible also that this hydrophobic fragment serves as a foundation for the formation of structured cluster in the unfolded state.

Using high-resolution NMR spectroscopy we conducted a comparative analysis of the structural and dynamic properties of the bacteriophage T5 endolysin (EndoT5) and its retro-form; i.e., a protein with the reversed direction of the polypeptide chain (R-EndoT5). We show that structurally, retro-form can be described as the molten globule-like polypeptide that is easily able to form large oligomers and aggregates. To avoid complications associated with this high aggregation propensity of the retro protein, we compared EndoT5 and R-EndoT5 in the presence of strong denaturants. This analysis revealed that these two proteins possess different internal dynamics in solutions containing 8M urea, with the retro-form being characterized by larger dimensions and slower internal dynamics. We also show that in the absence of denaturant, both forms of the bacteriophage T5 endolysin are able to interact with micelles formed by the zwitterionic detergent dodecylphosphocholine (DPC), and that the formation of the protein-micelle complexes leads to the significant structural rearrangement of polypeptide chain and to the formation of stable hydrophobic core in the R-Endo T5.

Background . Changes in the metabolic profiles of complex biological systems (cell, tissue, organ or organism) under normal and pathological conditions provide unique way to look at the physiological processes in living objects. Methods. The high-resolution NMR spectroscopy was used here to investigate seasonal changes in metabolite compositions of aqueous extracts from various tissues of several plants. Results. The birch sap is characterized by the high glucose and fructose levels. In addition to these sugars, relatively low concentrations of amino acids, organic acids, and alcohols were also present in the birch sap. During the early spring period, young growing leaves of the birch were characterized by the increased amounts of choline and scyllo-inositol. However, after the cessation of growth, the concentrations of these compounds in leaves decreased and remained unchanged even in the fallen leaves in November. Birch leaves also contained myoinositol. The linden leaves were also characterized by the presence of choline, high sugar levels, and very high concentrations of scyllo-inositol, whereas the aqueous extracts from the oak leaves contained only scyllo-inositol in addition to the high sugar levels. C onclusions. The results of this study suggest that the high-resolution NMR spectroscopy can be used to study the biochemistry of seasonal changes in woody plants. General Significance. The NMR spectroscopy is a powerful tool that can be used for the direct instrumental analysis of some metabolites in the plant tissues. Journal of Nature and Science, 1(5):e 8 8, 2015

The 3D-structure solution structure of the Zn2+-containing form of the bacteriophage T5 EndoT5-Zn2+is determined by the high-resolution NMR spectroscopy. The structural integrity of the entire molecule is controlled by the Zn2+binding.

We present here the concept of "in-plant" NMR and show that high-resolution NMR spectroscopy is suitable for the analysis of intact plants and can be used to follow the changes in the intraorganismal molecular composition over long time periods. The NMR-based analysis of the effect of different concentrations of heavy water on the aquatic plant Vesicularia dubyana revealed that due to the presence of specific adaptive mechanisms this plant can sustain the presence of up to 85% of D2O. However, it dies in 100% heavy water.

The paper deals with the NMR spectra obtained using preparations of five different human biological body fluids. Characteristic metabolite signals of blood, urine, tears, saliva, and sweat spectra have been determined and classified. The biological body fluid samples were used for search and identification of biomarkers of cardiovascular disease. Absolute functional biomarkers for diseases such as coronary heart disease (CHD) have not been recognized even in the case acute myocardial infarction. A hypothesis explaining reasons of lack of such markers has been formulated. The results of comparative analysis of blood and urine samples from humans and some laboratory animals are given. Identify and analyze signals of metabolites of pathogenic microflora and their dynamics in the urine from patients with urogenital diseases have been determined and analyzed and characteristic biomarkers have been recognized.