Biomedical subjects

N V Narizhneva

Publications and source records attributed to N V Narizhneva.

7 recordsLinked to original sources

PubMed1998

Effect of natural ligands on the structural properties and conformational stability of proteins.

The effect of natural ligands on the structural properties and conformational stability of proteins is reviewed. It is shown that the range of possible structural transformations induced in a protein molecule by ligand release is very wide and virtually does not depend on the nature of the protein or that of the ligands. Ligand-free forms of protein are classified from the viewpoint of structural property changes of a protein molecule.

Animals↗

PubMed1998

Decrease of dielectric constant transforms the protein molecule into the molten globule state.

The effect of organic solvents of different nature (alcohols, amides, and cyclic ethers) on the structural properties of beta-lactoglobulin was studied by circular dichroism and fluorescence spectroscopy. It is shown that the protein molecule undergoes at least two consecutive conformational transitions upon increase of the organic solvent concentration. Denaturation of the protein molecule occurs in the first step and a transition into the highly helical non-compact state in the second. In other words, under such conditions a compact denatured intermediate state is formed with a pronounced secondary structure, i.e., a molten globule-like state. It is shown that decrease of the dielectric constant of the media is responsible for structural changes of the protein molecule.

Animals↗

PubMed1997

Rigidity of human alpha-fetoprotein tertiary structure is under ligand control.

Comparative study of the natural ligand effect on structural properties and conformational stability of human alpha-fetoprotein (AFP) and its homologue, human serum albumin (HSA), was performed using several approaches, including circular dichroism, fluorescence spectroscopy, and scanning microcalorimetry. Here we show that denaturation of AFP, induced by the increase of temperature or urea concentration, is irreversible. We have established the fact that this irreversibility is caused by ligand release from the AFP molecule. Interestingly, the ligand-free form of AFP has no rigid tertiary structure but exhibits substantial secondary structure and high compactness. This means that the rigid tertiary structure of AFP is controlled by interaction with ligands, while their release results in transition of a protein molecule into a molten globule-like intermediate. In contrast, processes of HSA denaturation and unfolding are completely reversible. Release of ligands from HSA results only in a small decrease in stability but not transformation into the molten globule state.

Circular Dichroism↗

PubMed1997

Ligand-free form of human alpha-fetoprotein: evidence for the molten globule state.

By means of circular dichroism and fluorescence spectroscopy, viscometry and scanning microcalorimetry we have shown that the release of ligands from human alpha-fetoprotein (AFP) results in a considerable rearrangement of the protein molecule. Ligand-free form is practically as compact as the native molecule and has native-like content of secondary structure but no rigid tertiary structure. This means that the release of ligands transforms the AFP molecule into a molten globule state. Stripping the ligands from AFP is the irreversible process, i.e., native protein molecule cannot be reconstituted from the ligand-free form of AFP by adding back ligands. A possible functional role of such a structural transformation is discussed.

Humans↗

PubMed1997

Conformational transitions provoked by organic solvents in beta-lactoglobulin: can a molten globule like intermediate be induced by the decrease in dielectric constant?

BACKGROUND: It is known that nonnative states of protein molecules can exist in living cells and can be involved in a number of physiological processes. It has also been established that the membrane surface can be responsible for the partial denaturation of proteins due to negative charges on it. The local decrease in the effective dielectric constant of water near the organic surface has been suggested to be an additional driving force for protein denaturation in the membrane field, but data to confirm this suggestion were lacking. RESULTS: Conformational transitions induced in beta-lactoglobulin by methanol, ethanol, isopropanol, dimethylformamide and dioxane were studied by near and far UV circular dichroism, steady-state tryptophan fluorescence and fluorescence decay of 8-anilinonaphthalene-1-sulfonate (8-ANS). The existence of at least two noncoinciding cooperative transitions has been established in all solvent systems studied. The first of these transitions describes the disruption of rigid tertiary structure in protein molecules, while the second reflects the formation of an expanded helical conformation typical of proteins in concentrated organic solvents. This means that the organic solvents provoke the formation of a denatured intermediate state with pronounced secondary structure and native-like compactness. We show that the positions of maxima in fI versus dielectric constant dependence virtually coincide for all five solvent systems studied. CONCLUSIONS: The decrease in the dielectric constant of the solvent induces in beta-lactoglobulin an equilibrium intermediate state. This state, being denatured, is relatively compact and has pronounced secondary structure and high affinity for the hydrophobic fluorescent probe 8-ANS, i.e. possesses all the properties of the molten globule intermediate state.

Anilino Naphthalenesulfonates↗

PubMed1995

Structural properties of alpha-fetoprotein from human cord serum: the protein molecule at low pH possesses all the properties of the molten globule.

Structural studies of alpha-fetoprotein (AFP) from human cord serum have shown that a decrease in pH to 3.1 leads to a considerable conformational rearrangement of the protein molecule. The acid form of AFP belongs to the class of denatured conformations and fulfills all the requirements of the molten globule state. The possible functional role of such a transformation is discussed.

Anilino Naphthalenesulfonates↗

PubMed1995

[Structural properties of ribosomal protein S8 from the extreme thermophile Thermus thermophilus].

The gene of ribosomal protein S8 from the extreme thermophile Thermus thermophilus was expressed in E. coli using the strain BL21(DE3) and vector pET3-1. A method of isolating this protein from the super producing strain was developed, which makes it possible to obtain 8-12 mg of product from 11 of culture. The secondary structure of protein S8 was determined by using CD spectroscopy. The protein was shown to be highly resistant to denaturants.

Amino Acid Sequence↗