Biomedical subjects
Publications and source records attributed to L B Kaminir.
Using the decondensing effect of ethidium bromide and replicative (RBA) staining a high resolution map of cattle chromosomes was produced. The extent and distribution pattern of R(G) blocks were estimated quantitatively. The data thus obtained are correlated with the results of cytogenetic mapping in other mammalian species and in man.
Ultraviolet(254 nm)-irradiation-induced cross-linkages in ribosomal complexes allowed identification of proteins in contact with tRNA at different elongation steps. Both the set and the ratio of cross-linked proteins, i.e. the structural characteristics of the tRNA-binding sites of the ribosome, were shown to depend strongly not only on the position of the mRNA codon with which tRNA interacts as a component of a ribosomal complex, but also on its functional state, i.e. on the elongation step. A new classification of tRNA-binding sites of ribosome is suggested.
The squares of Ag-stained nucleolar organizing regions of metaphase chromosomes have been estimated by scanning their negative images on the film and computer data processing. The intercellular variation of the sum of squares of nucleolar organizing regiones of five individuals was studied. The coefficient of variation for these individuals varied from 11.2 to 24.6%. The analysis of the mean sum of squares of nucleolar organizing regiones per metaphase has revealed reliable differences for all the individuals. This value, therefore, can be taken as individual characteristics in the population research.
The effect of nerve growth factor (NGF), purified to homogeneity from bovine seminal plasma using HPLC, on the level of endogenous ADP-ribosylation in pheochromocytoma PC-12 cell line was studied. NGF caused a 30% inhibition of ADP-ribosylation in the cellular homogenate, a 25% inhibition during serum-free cultivation, and a 50% inhibition in the presence of serum in the culture medium. NGF inhibited ADP-ribosylation of several proteins, including a protein with molecular weight of 40,000, probably of membrane origin. A possibility of the interrelation between NGF and cyclase system via receptor-dependent ADP-ribosylation of regulatory components of the adenylate cyclase was discussed.
Ribosomal proteins participating in intersubunit RNA-protein contacts (directly interacting with RNA of the opposite subunit) were determined by means of ultraviolet-induced cross-links in pre- and post-translocated ribosomal complexes, as well as in the free 70 S ribosome (tight couple) of E. coli. In these 3 complexes at least L1 and L9 proteins interact with 16 S RNA, while S6, S9/11 and S15 react with 23 S RNA. All these proteins ('hinge-joint' proteins) are clustered on the small protuberance of the 50 S subunit and on the platform of the 30 S subunit. Reduction in the number of other (variable) intersubunit RNA-protein contacts in the course of transition from the tight couple to the pre- and, finally, to the post-translocated state, demonstrates gradual loosening of intersubunit interactions in 70 S ribosome. Such a loosening ('opening') of the 70 S ribosome is determined by conformational changes in ribosomal subunits and/or in their relative arrangement, conjugated with alteration of the functional state of the ribosomal complex.
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The paper contains a brief review of the studies involving application of computers, carried out at the Institute of Molecular Biology (investigation of the structure and dynamics of nucleic acids; modelling of the DNA-ligand interactions; analysis of the spectral data of different types: electron paramagnetic resonance, magnetic circular dichroism, absorption and fluorescence spectra; analysis of the thin-layer samples labelled by radioactive elements; chromosome analysis).
Proteins, directly interacting with tRNA in R- and A-sites of E. coli ribosome were determined by means of ultraviolet-induced RNA-protein cross-links. It is shown, that tRNAPhe in the R-site (upon enzymatic binding of the ternary complex Phe-tRNAPhe. X Tu X GMPPCP to ribosome) directly interact with factor Tu and ribosomal proteins S4, S5, S8 and L6, while in the A-site (upon binding of Phe-tRNAPhe X Tu X GTP, GTP hydrolysis, Tu release and transpeptidation)--with proteins S5, S10, L6, L16 and S13/S14/L27.
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Characteristics of electronic computers with respect to their use in molecular-biological investigations are briefly described. Several examples of using electronic computers in conformational investigations, in studies on the structure of biopolymers, chromatography, optico-spectral investigations, etc. are listed.