[Interaction of influenza A and B viruses with a carbon-containing sorbent]

The investigation demonstrated that influenza A and B viruses actively interacted with a sorbent obtained from modified oxygen-containing graphite via hydrothermal treatment irrespective of the antigenic structure of surface proteins. Virionic sorption occurred in a wide range of temperatures from 8 to 34 degrees C for 15 min or more. After interaction with the sorbent, the titer of a virus decreased 4- to 256-fold. The immobilized viruses were able to interact with homologous antibodies and immune sera. Desorption of viruses with the sorbent was extremely slight. In addition to viruses, the proteins of nonviral nature--those of allantoic hen embryo liquid, immune serum, and 1% bovine serum albumin--could be immobilized to the sorbent.

[Modified model of potato virus X coat protein structure]

We propose the modified model of the structure of coat protein (CP) subunits in filamentous virions of potato virus X (PVX). The model is similar to the one proposed by us in 2001 for the CP of another helical plant virus (potato virus A) belonging to other (potyvirus) group. In this model the PVX CP molecule consist of two main domains--a bundle of four alpha-helices located close to the virion long axis and a so-called RNP-fold (or abCd-fold) located near the virion surface. Basing on this model we suggest possible mechanism of described by J.G. Atabekov and colleagues structural transition ("remodeling") of the PVX virions resulting from their interaction with virus-specific TGB-1 protein.

[Changes in physicochemical characteristics of rabbit sclera as a result of reinforcement treatment]

It has been shown by biochemical analysis and differential scanning calorimetry that the connective tissue formed around a transplant as a result of sclero-reinforcing interference (capsula) is similar to intact sclera. The main component of newly formed capsules is collagen I whose fibers have a perfect structure and the amount of cross-links sufficient to provide normal thermomechanical properties. A fraction of collagen having thermally labile "immature" cross-links in capsules formed around the transplant impregraned with Panaxal has been detected by differential scanning calorimetry. It was suggested that fibroblasts in tissues of these capsules have a high synthetic activity.

A comparative study of functional properties of calf chymosin and its recombinant forms

The action of calf chymosin obtained from transgenic sheep milk and the recombinant protein expressed in yeast Kluyveromyces lactis (Maxiren) on fluorogenic peptide substrates, namely Abz-A-A-F-F-A-A-Ded, Abz-A-A-F-F-A-A-pNA, Abz-A-F-F-A-A-Ded, Abz-A-A-F-F-A-Ded, Abz-A-A-F-F-Ded, Abz-A-A-F-F-pNA, and heptapeptide L-S-F-M-A-I-P-NH2, a fragment of kappa-casein (the native chymosin substrate), was investigated. It has been established that transgenic chymosin and recombinant chymosin (Maxiren) differ from the native enzyme in their action on low molecular weight substrates, whereas there was no difference in enzymatic action on protein substrates. Pepstatin, a specific inhibitor of aspartic proteinases, inhibits the recombinant chymosin forms less efficiently than the native enzyme. Perhaps this is associated with local conformational changes in the substrate binding site of recombinant chymosin occurring during the formation of the protein globule.

Mass spectrometric sequencing and acylation character analysis of C-terminal anchoring segment from Influenza A hemagglutinin

Influenza A virus hemagglutinin (HA) is a major envelope glycoprotein mediating viral and cell membrane fusion. HA is anchored in the viral envelope by a light HA(2) chain containing one transmembrane domain and a cytoplasmic tail. Three cysteine residues in the C-terminal region, one in the transmembrane domain and two in the cytoplasmic tail, are highly conserved and potentially palmitoylated in all HA subtypes. The HA(2) C- terminal anchoring segments were extracted to organic phase from the bromelain-digested viruses (subviral particles) of three strains: A/X-31 (H3 subtype), A/Puerto Rico/8/34 (H1 subtype) and A/FPV/Weybridge/34 (H7 subtype). Their primary structures were assessed by matrix-assisted laser desorption/ionization time-of-flight time-of- flight mass spectrometry (MALDI-ToF-ToF MS). Trypsin-type protease-cleaved peptides prevailed over bromelain- cleaved ones in the peptide mixtures. All of them included transmembrane domains. Several distinctive features of the C-terminal HA(2) peptides acylation character were discovered by MALDI-ToF MS: 1) the peptides isolated from the viruses, which were digested by bromelain in the absence of beta-mercaptoethanol, were predominantly triply acylated; 2) the peptides were acylated not only by palmitic, but also by stearic acid residues; 3) the palmitate/stearate ratio was different for the three strains studied; 4) the A/FPV/Weybridge/34 strain has a priority to stearate binding. This fatty acid residue was discovered at the first of three conservative cysteine residues located in the transmembrane domain. It was found that presence of thiol reagent during preparation of subviral particles led to the appearence of the C-terminal HA(2) peptides acylated to different degrees. Triply, doubly, mono- and even unacylated peptides were detected. It was demonstrated that the thioester bond in the isolated acylpeptides was extremely sensitive to thiol reagents.

[Investigation of helical plant virus ribonucleoprotein structures with the help of tritium planigraphy and theoretical modeling]

The results of the studies of helical plant virus structures by tritium planigraphy (TP) method are discussed. TP method is based on bombardment of macromolecular objects with a stream of tritium atoms, followed by analysis of tritium label distribution along the macromolecule. By combining the TP data with the results of theoretical predictions of the protein structure, it turned out to be possible to propose a model of the coat protein structure in the virions of potato virus X (the type member of potexvirus group) and potato virus A (one of the members of potyvirus group). With the help of TP it also managed to find subtle differences in the coat protein structure between wildtype tobacco mosaic virus (strain U1) and its mutant with two amino acid substitutions in the coat protein and alter host specificity.

Influenza a Hemagglutinin C-terminal Anchoring Peptide: Identification and Mass Spectrometric Study

MALDI-TOF MS and N-terminal amino acid sequencing allowed us to identify several fragments of the C-terminal peptide of Influenza A hemagglutinin (HA) containing transmembrane domains (TMD). These fragments were detected in the organic phase of chloroform-methanol extracts from bromelain-treated virus particles. Heterogeneous fatty acylation of the C-terminus was revealed. Tritium bombardment technique might open an opportunity for 3D structural investigation of the HA TMD in situ.

Tritium planigraphy comparative structural study of tobacco mosaic virus and its mutant with altered host specificity

Spatial organization of wild-type (strain U1) tobacco mosaic virus (TMV) and of the temperature-sensitive TMV ts21-66 mutant was compared by tritium planigraphy. The ts21-66 mutant contains two substitutions in the coat protein (Ile21-->Thr and Asp66-->Gly) and, in contrast with U1, induces a hypersensitive response (formation of necroses) on the leaves of plants bearing a host resistance gene N' (for example Nicotiana sylvestris); TMV U1 induces systemic infection (mosaic) on the leaves of such plants. Tritium distribution along the coat protein (CP) polypeptide chain was determined after labelling of both isolated CP preparations and intact virions. In the case of the isolated low-order (3-4S) CP aggregates no reliable differences in tritium distribution between U1 and ts21-66 were found. But in labelling of the intact virions a significant difference between the wild-type and mutant CPs was observed: the N-terminal region of ts21-66 CP incorporated half the amount of tritium than the corresponding region of U1 CP. This means that in U1 virions the CP N-terminal segment is more exposed on the virion surface than in ts21-66 virions. The possibility of direct participation of the N-terminal tail of U1 CP subunits in the process of the N' hypersensitive response suppression is discussed.

Dysfunctionality of a tobacco mosaic virus movement protein mutant mimicking threonine 104 phosphorylation

Replication of tobacco mosaic virus (TMV) is connected with endoplasmic reticulum (ER)-associated membranes at early stages of infection. This study reports that TMV movement protein (MP)-specific protein kinases (PKs) associated with the ER of tobacco were capable of phosphorylating Thr(104) in TMV MP. The MP-specific PKs with apparent molecular masses of about 45-50 kDa and 38 kDa were revealed by gel PK assays. Two types of mutations were introduced in TMV MP gene of wild-type TMV U1 genome to substitute Thr(104) by neutral Ala or by negatively charged Asp. Mutation of Thr(104) to Ala did not affect the size of necrotic lesions induced by the mutant virus in Nicotiana tabacum Xanthi nc. plants. Conversely, mutation of Thr to Asp mimicking Thr(104) phosphorylation strongly inhibited cell-to-cell movement. The possible role of Thr(104) phosphorylation in TMV MP function is discussed.

Studying the spatial organization of membrane proteins by means of tritium stratigraphy: bacteriorhodopsin in purple membrane

The topography of bacteriorhodopsin (bR) in situ was earlier studied by using the tritium bombardment approach [Eur. J. Biochem. 178 (1988) 123]. Now, having the X-ray crystallography data of bR at atom resolution [Proc. Natl. Acad. Sci. 95 (1998) 11673], we estimated the influence of membrane environment (lipid and protein) on tritium incorporation into amino acid residues forming transmembrane helices. We have determined the tritium flux attenuation coefficients for residues 10-29 of helix A. They turned out to be low (0.04+/-0.02 A(-1)) for residues adjacent to the lipid matrix, and almost fourfold higher (0.15+/-0.05 A(-1)) for those oriented to the neighboring transmembrane helices. We believe that tritium incorporation data could help modeling transmembrane segment arrangement in the membrane.

Studying liposomes by tritium bombardment

Bilayer liposomes from a mixture of dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylethanolamine (DPPC: DPPE = 8:2, molar ratio) or DPPC labeled with 14C-DPPC (DPPC: 14C-DPPC) were bombarded with thermally activated tritium atoms. The tritiated liposomes were hydrolyzed by phospholipase C, and the tritium incorporation into different parts of the bilayer along its thickness was determined. The tritium flux attenuation coefficients were calculated for the headgroup (k1 = 0.176+/-0.032 A(-1)) and acylglycerol residue (k2 = 0.046+/-0.004 A(-1)) layers indicating a preferential attenuation of the tritium flux in the headgroup region and relative transparence of the membrane hydrophobic part. The finding is potentially important to apply tritium bombardment for investigation of spatial organization of transmembrane proteins in their native lipid environment.

In situ spatial organization of Potato virus A coat protein subunits as assessed by tritium bombardment

Potato virus A (PVA) particles were bombarded with thermally activated tritium atoms, and the intramolecular distribution of the label in the amino acids of the coat protein was determined to assess their in situ steric accessibility. This method revealed that the N-terminal 15 amino acids of the PVA coat protein and a region comprising amino acids 27 to 50 are the most accessible at the particle surface to labeling with tritium atoms. A model of the spatial arrangement of the PVA coat protein polypeptide chain within the virus particle was derived from the experimental data obtained by tritium bombardment combined with predictions of secondary-structure elements and the principles of packing alpha-helices and beta-structures in proteins. The model predicts three regions of tertiary structure: (i) the surface-exposed N-terminal region, comprising an unstructured N terminus of 8 amino acids and two beta-strands, (ii) a C-terminal region including two alpha-helices, as well as three beta-strands that form a two-layer structure called an abCd unit, and (iii) a central region comprising a bundle of four alpha-helices in a fold similar to that found in tobacco mosaic virus coat protein. This is the first model of the three-dimensional structure of a potyvirus coat protein.

[Differences in the spatial structure of an envelope protein from tobacco mosaic virus and its mutant, detected by tritium planigraphy]

Mutant ts21-66 of the tobacco mosaic virus (TMV) differs from the wild-type TMV-U1 by two mutations (Ile-21-->Thr and Asp-66-->Gly) in the coat protein (CP) gene and in symptoms produced in infected N' plants. The CP structure in TMV-U1 and ts21-66 virions was probed by tritium planigraphy. Compared with the wild-type CP, labeling of the N-terminal region of mutant CP was half as high and suggested its greater shielding. A role of this CP region in virus interactions with the N' resistance system is discussed.

Determination of biologically active low-molecular-mass thiols in human blood. II. High-performance capillary electrophoresis with photometric detection

A new high-performance capillary electrophoresis assay for aminothiols in human blood, including homocysteine, a marker of several human metabolism disorders, has been developed. Sample preparation involves conversion of disulfides to free thiols with triphenylphosphine, precipitation of proteins with sulfosalicylic acid, and conjugation of the thiols with monobromobimane. Derivatized thiols were separated in a sodium phosphate buffer using a fused-silica capillary (65 cm x 50 microm I.D.) at 30 degrees C. With the electric field of 250 V cm(-1), separation of homocysteine, glutathione and cysteine occurred at less than 10 min. Detection at 250 or 234 nm was used to confirm the monobimane-thiols peaks. The detection limit was approximately 5 nmol/ml for all labeled aminothiols. The proposed method for these compounds' analysis included simple sample preparation, high selectivity, good linearity (r2>0.999), high reproducibility (within-run precision for derivatized aminothiol peaks area RSD<5% for three times consequently injected sample); high reliability and the small volumes required for analysis made it suitable for clinical studies.

Qualitative and quantitative determination of biologically active low-molecular-mass thiols in human blood by reversed-phase high-performance liquid chromatography with photometry and fluorescence detection

The reversed-phase high-performance liquid chromatographic method employing photometry and fluorescence detection is described for the precise reproducible simultaneous measurement of total homocysteine (tHcy), cysteine (Cys), and glutathione (GSH) in human blood. Sample preparation involves conversion of disulfides to free thiols with triphenylphosphine, precipitation of proteins with trichloroacetic acid, conjugation of the thiols with monobromobimane (mBrB). The aminothiol assay is optimized by reduction and derivatization step conditions (pH, temperature and time of reactions) to obtain reliable quantitative results within the concentration range corresponding to normal and pathological levels of these thiols in human blood.

[L-arginine in the lacrimal fluid of patients with diabetic retinopathy and the possible role of nitric oxide in the pathogenesis of retinal ischemia]

The concentrations of 23 free amino acids and some other components (ammonium, urea, ethanolamine) were measured by liquid chromatography in the lacrimal fluid of 40 patients with diabetic retinopathy (DR) (15 with the preproliferative stage and 25 with proliferative stage) and 15 normal subjects. The mean level of L-arginine in DR patients was 3.5-5 times decreased in comparison with the control (1.2 +/- 0.4 vs. 6.1 +/- 1.5%, p < 0.005). The level of ornithine inversely correlated with the level of L-arginine. The mean level of ornithine in DR patients was increased twofold (12.3 +/- 1.0 vs 6.8 +/- 1.0% in the control, p < 0.005). The mean concentrations of other amino acids virtually did not change. Decreased level of L-arginine in the lacrimal fluid of DR patients may be indicative of increased utilization of this amino acid in retinal ischemia, which, according to the modern concept of DR pathogenesis, can be caused by activation of nitric oxide production. Measurement of L-arginine in the lacrimal fluid can serve as a simple noninvasive and reliable method for early diagnosis of ischemic changes in the retina.

The in situ spatial arrangement of the influenza A virus matrix protein M1 assessed by tritium bombardment

Intact influenza A virions were bombarded with thermally activated tritium atoms, and the intramolecular distribution of the label in the matrix protein M1 was analyzed to determine the in situ accessibility of its tryptic fragments. These data were combined with the previously reported x-ray crystal structure of the M1 fragment 2-158 [Sha, B. & Luo, M. (1997) Nat. Struct. Biol. 4, 239-244] and the predicted topology of the C domain (159-252) to propose a model of M1 arrangement in the virus particle.

Tritium planigraphy: from the accessible surface to the spatial structure of a protein

The method of tritium planigraphy, which provides comprehensive information on the accessible surface of macromolecules, allows an attempt at reconstructing the three-dimensional structure of a protein from the experimental data on residue accessibility for labeling. The semiempirical algorithm proposed for globular proteins involves (i) predicting theoretically the secondary structure elements (SSEs), (ii) experimentally determining the residue-accessibility profile by bombarding the whole protein with a beam of hot tritium atoms, (iii) generating the residue-accessibility profiles for isolated SSEs by computer simulation, (iv) locating the contacts between SSEs by collating the experimental and simulated accessibility profiles, and (v) assembling the SSEs into a compact model via these contact regions in accordance with certain rules. For sperm whale myoglobin, carp and pike parvalbumins, the lambda cro repressor, and hen egg lysozyme, this algorithm yields the most realistic models when SSEs are assembled sequentially from the amino to the carboxyl end of the protein chain.

Covalent chromatography of influenza virus membrane M1 protein on activated thiopropyl Sepharose-6B

The M1 protein of influenza virus is a highly hydrophobic polypeptide that is resistant to enzyme cleavage during incubation in water solutions. We show here that the M1 protein that is immobilized on an insoluble activated support (thiopropyl Sepharose-6B) by means of a thiol-disulfide exchange reaction acquires sensitivity to trypsin. After tryptic digestion noncysteine-containing peptides of M1 were removed by washing the support, while cysteine-containing ones were detached from the support by reduction. As a result, 24 unique tryptic peptides of M1 protein were clearly separated by reversed-phase high-performance liquid chromatography. The described method opens a new way to the investigation of functional properties of distinct domains of viral thiol proteins.

[Isolation and properties of serine proteinase PC from the Kamchatka crab, Paralithodes camtschatica--a proteolytic enzyme with broad specificity]

A homogeneous serine proteinase PC has been isolated from the Camchatka crab (Paralithodes camtschatica) hepatopancreas using affinity chromatography on arginine-Sepharose, protamine tryptic peptide-agarose and ion-exchange chromatography on Mono-Q, with a 68% yield. The enzyme is completely inhibited by diisopropylfluorophosphate, a typical inhibitor for serine proteinases. The molecular mass of the proteinase is 29 kDa, pI is 3.0. The proteinase splits Glp-Phe-Ala-pNA optimally at pH 7.5 and 47-55 degrees C; Km is 0.83 mM, kcat is 67 s-1. The enzyme is stable at pH 4-9. Proteinase PC possesses a broad substrate specificity and splits the peptide bonds formed by the carboxyl group of hydrophobic amino acids, arginine and lysine, in peptides and proteins. The enzyme hydrolyzes fibrin and collagen. Its N-terminal sequence, IVGGQEATP, reveals a 90% homology with analogous sequences of collagenolytic proteinases from other crab species.