PubMed Health⌕ Search

Biomedical subjects

T L Bushueva

Publications and source records attributed to T L Bushueva.

At least 19 recordsLinked to original sources
PubMed1995

Interaction of smooth muscle caldesmon with calmodulin mutants.

The interaction of avian smooth muscle caldesmon with calmodulin (CaM) was investigated by studying the ability of selected mutant calmodulins to induce fluorescence changes in caldesmon. Different types of CaM mutants were used including point charge mutants, cluster mutations, and mutations which alter the calcium binding of CaM. The caldesmon binding properties were only slightly affected by E84K-CaM or by the double mutation E84Q/E120Q-CaM. Affinity of calmodulin to caldesmon was decreased 2-4 times by point mutation G33V-CaM, double mutation E84K/E120K-CaM, deletion of residues 82-84, and by cluster mutations DEE118-120-->KKK or EEE82-84-->KKK. Mutations of the first (E31A-CaM) and the second (E67A-CaM) calcium binding sites reduced the affinity of calmodulin to caldesmon by at least 5-fold; in addition these calmodulin mutants exhibited smaller changes in the fluorescence spectra of caldesmon. Simultaneous mutation of the two negatively charged clusters of calmodulin EEE82-84-->KKK and DEE118-120-->KKK resulted in a more than 15-fold decrease in the affinity of calmodulin for caldesmon. The data indicate that charged and uncharged amino acids in both halves of CaM play an important role in the binding of calmodulin to caldesmon, and that Ca2+ binding must be maintained in the amino-terminal sites for maximal interaction with caldesmon.

Animals↗
PubMed1993

[Structure-functional properties of conjugates of proteins with polyalkylene oxides: study by a fluorescence method].

A fluorescent study of some structural and functional properties of conjugates of a number of proteins (bovine serum albumin, pyruvate kinase, alpha-chymotrypsin, and the two toxic proteins of plant origin--ricin and viscumin) with polyalkylene oxides (polyethylene glycol and pluronic) has been carried out. Analysis of the intrinsic protein fluorescence showed that the structure and stability of various protein conjugates to denaturing agents change only slightly: the conformational mobility of tryptophan residues accessible to the solvent decreases, whereas that of tryptophan residues localized in the protein regions of low polarity remains unchanged. Besides, the conjugates display a higher thermal stability in comparison with their native proteins. The fluorescence of 1-anilinonaphthalene-8-sulfonic acid and water insoluble 2',3',4',5'-tetrabenzoylriboflavin bound to the native and modified proteins indicated that modification of the proteins with polyalkylene oxides decreased the polarity and increased the viscosity of the microenvironment. Hence, this modification makes it possible to change some functional characteristics of the protein without causing any significant changes in its structure.

Anilino Naphthalenesulfonates↗
PubMed1991

Immunotoxin with mistletoe lectin I A-chain and ricin A-chain directed against CD5 antigen of human T-lymphocytes; comparison of efficiency and specificity.

Monoclonal anti-CD5 antibody was coupled to the enzymatically active subunit of plant toxin [either mistletoe lectin I (ML) or ricin]. The obtained conjugates proved to be selectively toxic to CD5-bearing target cells. The immunotoxin prepared from ML A-chain (MLA) was as toxic as native ML and approximately 80-fold more active than the corresponding conjugate with ricin A-chain (RTA). The comparative studies of the structural properties of isolated MLA and RTA were carried out using intrinsic fluorescence spectroscopy. The results showed similar properties for both proteins. No antigenic cross-reactivity against both toxins was detected when using polyclonal antibodies. The results suggest that MLA-antibody conjugates may be potential candidates for therapeutical use.

Antigens, CD↗
PubMed1991

[Recombination of micellar complexes of apolipoprotein A1--phosphatidylcholine in the presence of complex components].

Interaction of micellar complexes apolipoprotein A1--phosphatidyl choline (apoA1--DMPC and apoA1--EPC) with complex components: apoA1 (dansyl-A1) and phosphatydil cholines (DMPC, EPC and spin labelled PC) was studied in the absence of lipoproteins and plasma components. Recombination of the complexes (changes in complex sizes and stoichiometry) was shown to occur in the presence of the complex components. Interaction of lipid-free apoA1 with the complex is a fast process; incorporation of PC molecule takes place more slowly. This recombination is considered to be a kinetikally complicated process, the rate of recombination depending on PC exchange and interconversion.

Apolipoprotein A-I↗
PubMed1988

Caldesmon-calmodulin interaction. Study by the method of protein intrinsic tryptophan fluorescence.

Addition of calmodulin to caldesmon causes a concentration-dependent shortwave shift and an increase of fluorescence intensity of caldesmon tryptophan residues. The existence of a protein complex is confirmed by the increase of the caldesmon sedimentation coefficient s0(20,w) from 3.0 S to 4.5 S in the presence of calmodulin. These findings allow application of the method of protein intrinsic tryptophan fluorescence for quantitative study of unmodified caldesmon and calmodulin in solution. The affinity of the caldesmon-calmodulin interaction (Kass = 1.8 x 10(6) M-1, in 0.1 M-KCl at 25 degrees C) and Ca2+ requirement (half-maximum binding at 0.8 microM-Ca2+) determined by means of the fluorescence technique are in agreement with previously reported values, thus confirming the validity of the method. The same approach was further used to provide information about the nature of interactions stabilizing the caldesmon-calmodulin complex. Association of the proteins and dissociation of the complex were studied in different physicochemical conditions, including variation of pH, temperature and ionic strength and the addition of quenchers, denaturants and anticalmodulin drugs. The results obtained suggest that caldesmon tryptophan residues, together with charged groups, are involved in calmodulin binding. Hydrophobic, electrostatic and hydrogen interactions contribute to the stability of the protein complex, making it insensitive to variations of physicochemical conditions within physiological limits.

Animals↗
PubMed1988

Similarity of protein conformation at low pH and high temperature observed for B-chains of two plant toxins: ricin and mistletoe lectin 1.

A comparative study of subunits of two plant toxins, ricin (RC) and mistletoe lectin 1 (ML 1), has been undertaken. The study suggests that isolated B-chains of these toxins undergo structural transitions at low pH (from 5 to 4) and high temperature (45 degrees C), and as a result of the guanidine hydrochloride denaturing effect (to 3 M). Our results indicate that the protein conformation observed at low pH and high temperature are similar, though not identical. These conformations differ from the native one (pH 7, 25 degrees C), the protein in these conformations has a low fluorescence tryptophan intensity, and tryptophans are more exposed to aqueous solutions. However, these conformations differ also from the state unfolded by guanidine hydrochloride. An assumption is made that the partially denatured protein structure, exhibited at low pH and high temperature, is a functionally essential intermediate state of the toxin B-chain.

Hydrogen-Ion Concentration↗
PubMed1988

[Formation of micellar complexes of apolipoprotein A-I with dimyristoylphosphatidylcholine].

Structural changes of apolipoprotein AI from human plasma high density lipoproteins in 2-chloroethanol solutions were studied using spin label and fluorescence techniques. Reversible changes in spectral parameters occur in 2-chloroethanol concentration range 0-40% and are affected by dimyristoylphosphatidylcholine, of 2-chloroethanol concentration does not exceed 30%. Dialysis experiments demonstrated the absence of binding of monomer phosphatidylcholine with apolipoprotein AI. It thus follows that formation of complexes of apolipoprotein AI with dimyristoylphosphatidylcholine is caused by lipid micella aggregation.

Apolipoprotein A-I↗
PubMed1987

The effect of pH on the conformation and stability of the structure of plant toxin-ricin.

The effect of pH on the conformation of ricin and its A- and B-chains has been studied by measuring their intrinsic fluorescence. At pH 5.0 and 7.5, the structural stability of toxin and subunits was estimated according to the denaturing action of guanidine hydrochloride. It was demonstrated that the fluorescence of native toxin and catalytic A-subunit does not depend significantly on pH in the range pH 3-8, whereas ricin B-chain undergoes a structural transition at pH less than 5.0. The structural stability of ricin and isolated chains differs significantly at pH 7.5 and 5.0; the structural stability of ricin and the A-chain increases, whereas that of the B-chain decreases.

Hydrogen-Ion Concentration↗
PubMed1978

Relationship of thermal quenching of protein fluorescence to intramolecular structural mobility.

Temperature dependence (over the range from 5 to 75 degrees C) of the fluorescence quantum yield--the parameter sensitive to the rapid (ns) mobility--has been investigated. For native proteins containing 1--2 fluorescing chromophores this dependence in the non-denaturing temperature range can be described by the equation 1/q = a + b . T/eta (a and b are temperature-independent constants, T is the temperature (K), eta is the viscosity of water, (cP). The linearity of the plot of 1/q vs. T/eta probably indicates that the internal mobility of different parts of the protein globule is limited by the diffusion of the molecules of the solvent. The peculiarity of individual protein structures is reflected by various absolute values of the constants of quenching rates. The results of the studies indicate that an analysis of the temperature dependence of the protein fluorescence quantum yield (thermal quenching curves) might be a new experimental approach to the study of the mobility of protein structures. The thermal quenching curves of proteins could be used as a measure of the temperature dependence of the rapid reverse structural mobility.

Models, Biological↗
PubMedDate not supplied

[Interaction of the toxic plant protein--ricin, with model membranes. A fluorescence method of study].

The fluorescence method has been used to investigate ricin and its isolated subunits interaction with some model membranes. Three liposome types were used as a model of biological membrane: 1) liposomes constructed from lecithin and cholesterol (9:1, M:M) 2) from ganglioside receptors GM1 and 3) from the mixture of GM1, lecithin and cholesterol (1:9:1). Interaction of the protein with liposome evokes changes in the parameters of both intrinsic protein fluorescence and fluorescence of the covalently bound dansyl. Binding constants were calculated from a decrease of the intrinsic fluorescence intensity as well as from the changes in the dansyl rotation anisotropy. Measurements were carried out at neutral and acidic pH. There was good correlation of the results obtained by different methods. It was shown that association constants were different for intact ricin and its subunits. The constants also depend on liposome composition and pH of the solution. The present study has demonstrated that interaction of ricin with liposome is accounted for not only by receptor centers but also by other hydrophobic regions of ricin that are inaccessible in the native toxin and may represent the region of the subunits interaction.

Cholesterol↗
PubMedDate not supplied

[Elongation factor EF-Ts interacts with the aminoacyl-tRNA.EF-Tu.GTP complex].

The fluorescence polarization technique has been used to study the interaction of the EF-Ts dansyl derivative with EF-Tu after nucleotide exchange and binding of the aminoacyl-tRNA to EF-Tu.GTP. It is shown that the ternary complex formation results in the increase of EF-Ts affinity to EF-Tu and EF-Ts remains bound to EF-Tu up to the GTP hydrolysis stage on the ribosome.

Fluorescence Polarization↗
PubMedDate not supplied

[Interaction of perch fucolectin with Lewis antigens].

Interaction of fucolectin of perch Perca fluviatilis (PFL) with a set of Lewis antigens was studied by monitoring changes in its tryptophan fluorescence. PFL bound Le(c) (H type 1)-pentasaccharide (Ka = 6.6 x 10(3) M(-1)) and H type 6-trisaccharide (Ka = 2.5 x 10(3) M(-1)); essentially weaker, with Le(b)-hexasaccharide (Ka = = 4.0 x 10(2) M(-1)); and failed to interact with Le(a)-, Le(x)-, and Le(d)-containing oligosaccharides. PFL belongs to a new type of the fucolectins recognizing H-disaccharide Fuc alpha1-2Gal within various antigens, including H type 1/2 and Le(b).

Animals↗