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Biomedical subjects

Iu N Chirgadze

Publications and source records attributed to Iu N Chirgadze.

At least 19 recordsLinked to original sources
PubMed1979

[Isolation and structural properties of membrane-bound Na+,K+- adenosine triphosphatase from pig kidney].

A technique for isolation of large amounts of homogeneous Na+, K+-ATPase lipid-protein complex from pig kindney has been developed. The purity of the preparation as determined by the protein component is 96-98%, the large to small subparticle ratio being 4 : 1. The protein and lipid parts of the preparation have approximately the same mass. The enzyme activity is 1600-1900 mcmoles of inorganic phosphate released per mg of protein per hour. The protein secondary structure in a heavy water solution has been studied by infrared spectroscopy in the region of the main amide bands. It has been shown that about 20% of the peptide groups form highly ordered alpha-helical regions and about 25% are found in the pleated sheet structure with an antiparallel packing of the chains. The regions with a regular structure are mainly located in the protein component regions, inaccessible for water and are presumably involved in the formation of the hydrophobic core of the molecule. The major part of the protein structure (approximately 55%) is non-ordered and is easily accessible for water molecules.

Animals↗
PubMed1979

[Conformational rearrangements of bacteriophage T4 lysozyme during its binding to the inhibitor].

The structural changes of bacteriophage T4 lysozyme during its binding to the inhibitor, i. e. disaccharide-tetrapeptide N-acetylglucosaminyl-N-acetylmuraminyl - L - alanyl-gamma-D-glutaminyl - mesodiaminopimelyl-D-alanine) isolated from Escherichia coli cell wall have been studied. During the inhibitor binding to the protein the degree of helicity decreases by approximately 14% as was shown using the circular dichroism technique. The changes in optical properties of tryptophane, tyrosine and phenylalanine residues detected by UV difference and fluorescence spectroscopy have been observed. Based on the experimental data and a comparison of spatial organization of phage T4 lysozyme and chicken egg-white lysozyme made it possible to develop a structural model of phage T4 lysozyme functioning. This model may account for the differences in specificity of action of bacteriophage T4 and chicken egg-white lysozymes and allows to establish the role of the "extra" part of phage lysozyme. According to the model, at the first stage of binding the peptide part of the substrate comes in contact with the "upper" (with respect to the cleft) part of the protein molecule (residues 106--116 and 135--140). This results in rearrangement of the molecule, with opening of the cleft at the second stage. This makes possible the access of the polysaccharide part of the substrate of the active site and a subsequent hydrolysis of the beta (1 leads to 4) glycoside bond.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMedDate not supplied

[Formation of recognition site in transcription factors: repressor of phage lambda and a murine immunoglobulin factor].

IPolar interactions between protein and the major groove of double-stranded DNA have been analyzed on the basis of a structural study of the complexes formed by two transcription factors: phage lambda repressor and murine immunoglobulin transcription factor NF kappa B-p50. Two identical molecules of these two factors form two binding sites within two different parts of a single DNA molecule. This allows one to study formation of the recognition module by comparing the binding pattern of two different parts of the DNA operator. We have shown that formation of the DNA-binding sites for the three structurally different protein domains (one in repressor and two in the immunoglobulin factor) involves polar residues selected from the largest polar cluster on the surface of the protein molecule. It was also shown that the same polar residues bind with different points of DNA sites. This result provides understanding of the recognition module adaptation to varying nucleotide sequence of the operator sites and shows the way of binding site formation.

Animals↗
PubMedDate not supplied

[Functionally important sites in the elongation factor EF-Tu from Thermus aquaticus: analysis of fine structural changes upon binding of guanosine-3'-triphosphate and guanosine-3'-diphosphate].

High-resolution data were used to analyze conformational changes of the main chain in two functional states of the ribosome elongation factor EF-Tu from Thermus aquaticus: the inactive state with guanosine-3'-diphosphate and the active state with guanosine-3'-triphosphate. Earlier only major changes in the effector loop of the domain I were determined. In this paper, all rearrangements in the main chain were observed upon shifting of C alpha-atoms from 1 to 8 A for each of the three protein domains. It was shown that these changes occur in numerous regions. New regions of changes were found, and they were located mostly in the loops of protein domains. Some of them are in the regions of interdomain interactions, others correlate with the known functionally important regions of EF-Tu binding with EF-Ts, aminoacyl-tRNA and the ribosome. Most changes induced by the conformational signal transfer from the guanosine-3'-triphosphate binding site occur just in the regions that are important for further stages of the factor functioning. The signal is transferred from domain I to domains II and III via interdomain contacts, predetermining fine fitting of functionally important regions to be involved in the following stages of the elongation cycle. The greatest part of the detected changes occurs in conservative residues of the whole family of bacterial factors, and only some of them are specific. This approach may prove useful for predetermining potential functionally important sites in other proteins.

Guanosine Diphosphate↗
PubMedDate not supplied

[Definitive role of polar residue clusters in B-DNA major groove recognition by protein factors].

The 3D structural data for a number of protein-DNA complexes were used to analyze the regions of specific contact with the major groove of B-DNA double helix. The set included seven nonhomologous complexes featuring 12 DNA-binding domains of transcription factors and regulatory factors. The protein domains differed in structure, contained different motifs in the binding region, and broadly varied in chain length, from 30 to 200 residues. Protein-DNA interaction was assessed as hydrogen bonding between polar atoms and van der Waals contacts between nonpolar atoms. The binding sites were formed mainly through polar side chain interactions. On average, the recognition site comprises seven residues, six of them polar. The contact residues nearly always belong to a largest polar cluster of the protein. Thus one can think that the protein polar residue clusters play an important role in forming the protein-DNA recognition module.

Adhesins, Bacterial↗