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S Stoeva

Publications and source records attributed to S Stoeva.

64 records · Page 4Linked to original sources
PubMed1991

The primary structure of the hemoglobin from the aardwolf (Proteles cristatus, Hyaenidae).

The hemoglobin of the aardwolf (Proteles cristatus) contains only one component. In this paper, we are presenting its primary structure. The globin chains were separated by high-performance liquid chromatography and the sequences determined by automatic liquid and gas-phase Edman degradation of the chains and their tryptic peptides. The alpha- as well as the beta-chains show 20 exchanges compared with the corresponding human chains. The difference to the masked palm civet (Paguma larvata) and the spotted hyaena (Crocuta crocuta) is marked by 16 and 4 replacements in the alpha-chains and by 10 and 1 in the beta-chains, thus supporting the hyaenid character of the aardwolf. The exchanges at contact positions are shared by other carnivoran hemoglobins.

Amino Acid Sequence↗
PubMed1990

Primary structure of a zinc protease from Bacillus mesentericus strain 76.

The amino acid sequence of the neutral zinc protease from Bacillus mesentericus strain 76 (MCP 76) has been determined by using peptides derived from digests with trypsin, chymotrypsin, and cyanogen bromide and from cleavage with o-iodosobenzoic acid. The peptides were purified by means of gel filtration and reversed-phase high-performance liquid chromatography and analyzed by automatic sequencing. The protein contains 300 amino acid residues. It proved to be identical with the neutral protease deduced from the DNA precursor sequence of Bacillus subtilis. The residues for zinc and substrate binding are conserved, whereas the number of calcium binding sites is reduced compared to thermolysin. A classification of the neutral zinc protease is discussed.

Amino Acid Sequence↗
PubMed1989

Proteolytic specificity of the neutral zinc proteinase from Bacillus mesentericus strain 76 determined by digestion of an alpha-globin chain.

The proteolytic specificity of the neutral zinc proteinase from Bacillus mesentericus strain 76 (MCP 76)/Bacillus subtilis was determined by using the alpha-chain of walrus hemoglobin as substrate. The resulting peptides were fractionated by gel filtration and than isolated by reversed-phase HPLC. The peptides were identified on the basis of their amino-acid compositions and aligned with the known sequence of the walrus alpha-chain. The proteolytic specificity of MCP 76, deduced from the experimental cleavage pattern is compared to that of thermolysin. The amino-acid residues in positions P1 and P'1 on both sides of the scissible bond are considered as most important for the cleavage. MCP 76 prefers leucine, valine, phenylalanine and threonine in position P'1 as well as lysine, threonine, leucine and alanine in position P1 and thus differs from thermolysin which shows no preference for threonine in P'1 and accepts numerous amino-acid residues of different type in P1.

Amino Acid Sequence↗
PubMedDate not supplied

A novel beta-thymosin from the sea urchin: extending the phylogenetic distribution of beta-thymosins from mammals to echinoderms.

The study of the phylogenetic distribution of the beta-thymosin family is important to elucidate its biological function further. A new thymosin, designated as thymosin beta 14, consisting of 40 amino acid residues and with a molecular weight of 4537 Da as determined by ion spray mass spectrometry, was isolated from the sea urchin. The N-terminus of this polypeptide is blocked by an acetyl group as found by matrix-assisted laser desorption mass spectrometric and amino acid analysis. The primary structure was elucidate by Edman degradation of the HPLC-purified thymosin beta 14 fragments produced by digestion with endoproteinase Asp-N and trypsin. Sequence comparison reveals that thymosin beta 14 is 73% homologous to thymosin beta 4, obtained from calf thymus. By isolating and characterising the structure of thymosin beta 14 from the sea urchin, an invertebrate, substantial knowledge about the phylogenetic distribution and evolution of beta-thymosins is gained.

Amino Acid Sequence↗
PubMedDate not supplied

Application of capillary electrophoresis in peptide research.

Comparison of high performance liquid chromatograms (HPLC) with capillary electrophoresis shows the latter to be superior in many cases owing to rapid separation, high resolution and high sensitivity. This is demonstrated with two examples (i) the isolation of natural peptides from bovine tissue and (ii) characterization of a synthetic peptide mixture with the natural sequence (fragment) of the human immunodeficiency virus (HIV) transmembrane glycoprotein gp 41 env.

Amino Acid Sequence↗
PubMedDate not supplied

Penaeus monodon (tiger shrimp) hemocyanin: subunit composition and thermostability.

Penaeus monodon (class Crustacea, order Decapoda) is one of the largest shrimps of the Penaeidea family from the Indo-West Pacific region. The dioxygen-transporting protein hemocyanin, isolated from the hemolymph of this invertebrate, is composed of three 75-76 kDa structural/functional subunits designated as Pm1, Pm2 and Pm3. The N-terminal sequences of the chains were determined and compared with those of other decapodan hemocyanin subunits. Pm2 and Pm3 are highly homologous and electrophoretically undistinguishable polypeptides. In comparison to Pml, they have an extension of six residues. Pm1 is closely related to the subunit Pv2 of the Penaeus vannamei hemocyanin. Probably, subunits like Pm1 and Pv2 are family-specific for the Penaeidea hemocyanins and the other subunits are species-specific. Comparison of N-terminal sequences of respiratory proteins from the sub-orders Natantia and Reptantia demonstrated family- and sub-order-specific sequences. A melting point of 69 degrees C, lower than those for the di-hexameric decapodan hemocyanins, was determined from the temperature dependence of ellipticity of the mono-hexameric Penaeus monodon hemocyanin. Thermostability of decapodan hemocyanins depends on their aggregation state.

Amino Acid Sequence↗
PubMedDate not supplied

Viviparus ater hemocyanin: investigation of the dioxygen-binding site and stability of the oxy- and apo-forms.

The active site of Viviparus ater (mollusc) hemocyanin was investigated using the fact that the binding of dioxygen to the binuclear copper-containing sites of hemocyanins is connected with the appearance of specific dichroic bands which are very sensitive to changes in the structrure and polarity of the environment. Oxy-Viviparus ater hemocyanin exhibits near UV and visible circular dichroism spectra different from those of other molluscan and arthropodan hemocyanins. These differences are due probably to variations in the geometry or charge distribution in the dioxygen binding sites of the compared proteins. The thermostability of Viviparus ater hemocyanin and the significance of the copper-dioxygen system for the stability were also investigated. "Melting" temperatures, Tm, of 77 degrees C for the oxy-hemocyanin and 57 degrees C for the apo-protein were calculated from the denaturation curves which demonstrates the considerable role of the binuclear active site for the thermostability. Viviparus ater hemocyanin is more thermostable than other hemocyanins for which data are published.

Amino Acids↗
PubMedDate not supplied

[Petroleum-oxidizing microflora of the Arctic seas of the USSR].

Active petroleum-oxidizing bacteria of the USSR arctic seas are represented by Mycobacterium mucosum (non-colored), Mycobacterium phlei and Mycobacterium brevicale (red-orange) which inhabit the Yenisei Bay, the Kara Sea and the Laptev Sea. Vertical distribution of the petroleum-oxidizing mycobacteria is characterized by substitution of non-coloured forms for coloured ones with depth: "white" strains are found mainly in the surface layer while red and yellow-orange strains are detected in deep water layers and near the bottom.

Arctic Regions↗
PubMedDate not supplied

The prognostic value of alpha-thymosins in breast cancer.

The prognosis of breast cancer is of major clinical importance and several histopathological, biochemical and immunological variables have been reported to be useful prognostic factors. In the present study, we investigated the clinical significance of the levels of alpha-thymosins in relation to established prognostic factors, both in breast cancer and non-malignant breast lesions, alpha-thymosin levels were measured in breast tissue extracts by specific radioimmunoassays (RIAs) developed for human prothymosin alpha (ProT alpha) and parathymosin alpha (ParaT alpha) and were found to be significantly higher (up to 17.2-fold) in malignant but not in benign breast lesions, as compared to the values of the neighbouring tissues. When alpha-thymosin levels of the tumor samples were correlated with various known prognostic parameters a statistically significant correlation (p < 0.05) was observed between the levels of ProT alpha in malignant tissues to the grade of cancer and the lymph node status of the patient. An association between ProT alpha levels with increase in risk of death from breast cancer was also noticed. These results suggest that the expression of alpha-thymosins in human breast cancer a) depends on the proliferation status of the tumor, b) associates with established prognostic factors describing the metastatic potential of the tumor and c) is related to the overall survival of the patient. The fact that such relationships hold only for cancer tissues encourages the future use of alpha-thymosins as potent prognostic factors in breast cancer.

Adult↗