Biomedical subjects

S F Barbashov

Publications and source records attributed to S F Barbashov.

25 records · Page 2Linked to original sources

PubMedDate not supplied

[X-ray structural study of leucine aminopeptidase with a resolution of 4 Angstroms].

An X-ray crystallographic structure determination has been carried out on bovine lens leucine aminopeptidase at 4.0 A resolution by using a combination of isomorphous replacement and solvent flattening. The two heavy atom derivatives used were obtained by soaking crystals in ethyl mercury chloride, which bound at four sites, and phenyl mercury acetate, which bound at one site in the monomer. The electron density map reveals that the enzyme hexameric oligomer, arranged in 32 symmetry, has a triangular barrel appearance and dimensions, of height 88 A and maximal width 118 A in barrel equatorial plane. Each subunit in an elongated ellipsoid of approximate length 92 A. Subunits contacts have been described. From an analysis of the map each subunit appears to contain some 36% alpha-helix and is organized into two distinct globular domains. Direct location of zinc cluster and competitive inhibitor binding site are presented.

Animals↗

PubMedDate not supplied

[The use of monoclonal antibodies against insulin for isolation of proteins inhibiting the cell growth].

Extracts of pig kidneys or germinated soya beans after preliminary steps were affinity chromatographied on Sepharose containing cyanogen bromide immobilized monoclonal antibodies to pig insulin. The material bound to the affinity column was separated by HPLC resulting in one homogeneous protein from each source. Both proteins have been shown to inhibit DNA synthesis in cultured embryonic human fibroblasts and VERO fibroblasts. The effect of pig kidney protein was potentiated by insulin. Soya and pig proteins were characterized by the following parameters: molecular weights of 8.5 and 10.3 kD, apparent constants of dissociation with rat liver plasma membranes of 4.7 x 10(-8) M and 9.8 X 10(-8) M, respectively. The soya proteins competed for the binding sites on plasma membranes with insulin whereas the pig protein did not. The N-terminal amino acid sequences of 20 residues were determined for both proteins. Comparison of these sequences with known protein sequences was performed. A 30-40% primary structure homology of the studied fragment of soya bean protein with the fragments of some oncogenic viruses proteins and transforming proteins was revealed.

Amino Acid Sequence↗

PubMedDate not supplied

[Isolation and study of the properties of an insulin-binding protein from the blood serum].

A question of the existence of blood proteins binding unmodified insulin has remained open for many years. This paper is devoted to the description of a method of isolation and characteristics of the insulin-binding protein (IBP) isolated from rat and human blood sera. The level of IBP in the serum was 0.12-0.15 mg/ml. The protein was referred to IgG basing on the data of electrophoresis under denaturing conditions, immunoelectrophoresis and immunoenzymatic analysis. The constant of protein association with insulin varied with regard to a source within 1.5.10(-7) to 2.5.10(7) M-1. The studied protein bound both 125I-modified and unmodified insulin preparations. The calculation based on IBP parameters, showed that no less than half of the blood insulin must be in a bound condition. The capacity of such insulin-binding system is rather great and is capable of leveling down sharp changes in a blood insulin concentration.

Animals↗

PubMedDate not supplied

[Properties of mouse spleen residual condensed chromatin associated with the nuclear matrix].

Properties of condensed residual chromatin of mouse spleen, a component of residual nuclear structures, were studied. Extraction of the structures with buffers of different NaCl concentrations showed that the condensed chromatin consists of condensed nucleosomal chains. On increasing the ionic strength the complexes gradually fell apart into separate nucleosomal chains. DNA of condensed chromatin was accessible to staphylococcal nuclease and DNAase I, but digestion of this DNA was not accompanied by solubilization of the residual chromatin. Besides the essentially decreased total content of nonhistone chromosomal proteins the condensed chromatin practically did not contain HMG proteins. The nucleosome repeat length of this chromatin was shorter than that of chromatin solubilized by staphylococcal nuclease.

Animals↗

PubMedDate not supplied

[Residual chromatin of mouse spleen nuclei after intensive nuclease treatment. Isolation and properties].

Two-step treatment of mouse spleen nuclei with staphylococcal nuclease was used to isolate residual nuclear structures lacking a considerable part of chromation. Partial disruption of the nuclear envelope after the first step of digestion was shown to be essential for obtaining residual nuclear structures. Isolated residual nuclear structures contained condensed chromatin (residual chromatin) which was not solubilized upon additional staphylococcal nuclease treatment and amounted to approximately 20% of total nuclear chromatin. Residual chromatin was almost deprived of nonhistone chromosomal proteins. It contained a full complement of histones and consisted of nucleosomal chains having different lengths--from one to 50-60 nucleosomes. Some of the condensed chromatin chains were anchored to the nuclear matrix.

Animals↗

PubMedDate not supplied

[Localization of histone H1 in chromatin. Cross-linking of the N- and C-terminal halves of the molecule with bifunctional reagents].

Mutual arrangement of histone H1 molecules was studied in calf thymus nuclei, extended chromatin and chromatin, isolated and kept in 8 M urea. Histone H1 dimers crosslinked with methyl 4-mercaptobutyrimidate were digested with chymotrypsin and crosslinked fragments obtained were analysed by diagonal gel electrophoresis. In all chromatins tested the N- and C-terminal parts of the H1 molecules were crosslinked in all possible combinations, i.e. C-C, C-N and N-N. These and related data obtained earlier indicate, that the proximity of histone H1 molecules in chromatin is determined by the structure of nucleosomal chain itself and not by chromatin superstructure. The results also suggest that the H1A and H1B subfractions of histone H1 are interspersed in extended nucleosomal chains.

Animals↗

PubMedDate not supplied

[Localization of histone H1 in chromatin. Cross-linking of central globular regions of H1 molecules with a bifunctional reagent].

Mutual arrangement of histone H1 molecules and central globular parts of H1 was studied by crosslinking with a reversible bifunctional reagent. The yields of histone H1 dimers and dimers of it's globular fragment in nuclei and isolated chromatin were similar. In the presence of 8 M urea the yield of the H1 dimers was approximately threefold decreased, dimers of globular fragment being practically absent. The data suggest that the proximity of H1 molecules in nuclei is stipulated by a structure of a nucleosomal chain itself and not by chromatin superstructure. The results are in accord with the "head" to "head" histone H1 orientation within the nucleosomal chain and do not support participation of the central globular region of H1 molecule in chromatin condensation. A model of H1 arrangement in extended nucleosomal chain is proposed.

Animals↗