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Yana K Reshetnyak

Publications and source records attributed to Yana K Reshetnyak.

7 recordsLinked to original sources
PubMed2007

Topography studies on the membrane interaction mechanism of the eosinophil cationic protein.

The eosinophil cationic protein (ECP) is an antipathogen protein involved in the host defense system. ECP displays bactericidal and membrane lytic capacities [Carreras et al. (2003) Biochemistry 42, 6636-6644]. We have now characterized in detail the protein-membrane interaction process. All observed fluorescent parameters of the wild type and single-tryptophan-containing mutants, as well as the results of decomposition analysis of protein fluorescence, suggest that W10 and W35 belong to two distinct spectral classes I and III, respectively. Tryptophan residues were classified and assigned to distinct structural classes using statistical approaches based on the analysis of tryptophan microenvironment structural properties. W10 belongs to class I and is buried in a relative nonpolar, nonflexible protein environment, while W35 (class III) is fully exposed to free water molecules. Tryptophan solvent exposure and the depth of the protein insertion in the lipid bilayer were monitored by the degree of protein fluorescence quenching by KI and brominated phospholipids, respectively. Results indicate that W35 partially inserts into the lipid bilayer, whereas W10 does not. Further analysis by electron microscopy and dynamic light scattering indicates that ECP can destabilize and trigger lipid vesicle aggregation at a nanomolar concentration range, corresponding to about 1:1000 protein/lipid ratio. No significant leakage of the vesicle aqueous content takes place below that protein concentration threshold. The data are consistent with a membrane destabilization "carpet-like" mechanism.

Eosinophil Cationic Protein↗
PubMed2006

Mechanism of formation of actomyosin interface.

Force generation in muscle results from binding of myosin to F-actin. ATP binding to myosin provides energy to dissociate actomyosin complex while the hydrolysis of ATP is needed for re-binding of myosin to F-actin. At the end of each cycle myosin and actin form a tight complex with a substantial interface area. We investigated the dynamics of formation of actomyosin interface in presence and absence of nucleotides by quenched flow cross-linking technique. We showed previously that myosin head (subfragment 1, S1) directly interacts with at least two monomers in the actin filament. The quenched flow cross-linking experiments revealed that the initial contact (in presence or absence of nucleotides) occurs between loop 635-647 of S1 and 1-12 N-terminal residues of one actin and, then, the second contact forms between loop 567-574 of S1 and the N terminus of the second actin. The distance between these two loops in S1 corresponds to the distance between N termini of two actins in the same strand (53 A) but is smaller than that between two actins from the different strands (102 A). The formation of the actomyosin complex proceeds in ordered sequence: S1 initially binds to one actin then binds with the second actin located in the same strand but probably closer to the barbed end of F-actin. The presence of nucleotides slows down the interaction of S1 with the second actin, which correlates with recently proposed cleft movement in a 50 kDa domain of S1. The sequential mechanism of formation of actomyosin interface starting from one end and developing towards the barbed end might be involved in force generation and directional movement in actin-myosin system.

Actins↗
PubMed2006

Translocation of molecules into cells by pH-dependent insertion of a transmembrane helix.

We have previously observed the spontaneous, pH-dependent insertion of a water-soluble peptide to form a helix across lipid bilayers [Hunt, J. F., Rath, P., Rothschild, K. J. & Engelman, D. M. (1997) Biochemistry 36, 15177-15192]. We now use a related peptide, pH (low) insertion peptide, to translocate cargo molecules attached to its C terminus across the plasma membranes of living cells. Translocation is selective for low pH, and various types of cargo molecules attached by disulfides can be released by reduction in the cytoplasm, including peptide nucleic acids, a cyclic peptide (phalloidin), and organic compounds. Because a high extracellular acidity is characteristic of a variety of pathological conditions (such as tumors, infarcts, stroke-afflicted tissue, atherosclerotic lesions, sites of inflammation or infection, or damaged tissue resulting from trauma) or might be created artificially, pH (low) insertion peptide may prove a useful tool for selective delivery of agents for drug therapy, diagnostic imaging, genetic control, or cell regulation.

Amino Acid Sequence↗
PubMed2004

Conformational and enzymatic changes of 20S proteasome of rat natural killer cells induced by mono- and divalent cations.

We have been investigated the relation between activation of "neutral" and "acidic" chymotrypsin-like (ChT-L) activity and conformational changes in the 20S proteasome complex from the rat natural killer (NK) cells induced by SDS, mono- and divalent cations. The conformational changes were monitored by tryptophan fluorescence and light scattering. It was revealed that the changes in the maximum position and contribution of the short-wavelength spectral component correlated with the alteration of ChT-L activity of the proteasome. Statistical analysis was applied to assign the fluorescence components with tryptophan residues based on the classification of calculated structural parameters of the environment of tryptophan fluorophores in protein. It was proposed that the emission of W13 from alpha6-subunit located near the cluster of highly conserved proteasome residues is mostly sensitive to the activation of the enzyme. We concluded that the expression of maximal ChT-L activity of 20S proteasome is associated with the conformational changes occurs in this cluster that lead to the proteasome open conformation, allowing substrate access into the proteolytic chamber.

Animals↗
PubMed2004

Folding kinetics and structure of OEP16.

The chloroplast outer membrane contains different, specialized pores that are involved in highly specific traffic processes from the cytosol into the chloroplast and vice versa. One representative member of these channels is the outer envelope protein 16 (OEP16), a cation-selective high conductance channel with high selectivity for amino acids. Here we study the mechanism and kinetics of the folding of this membrane protein by fluorescence and circular dichroism spectroscopy, using deletion mutants of the two single tryptophanes Trp-77-->Phe-77 and Trp-100-->Phe-100. In addition, the wild-type spectra were deconvoluted, depicting the individual contributions from each of the two tryptophan residues. The results show that both tryptophan residues are located in a completely different environment. The Trp-77 is deeply buried in the hydrophobic part of the protein, whereas the Trp-100 is partially solvent exposed. These results were further confirmed by studies of fluorescence quenching with I(-). The kinetics of the protein folding are studied by stopped flow fluorescence and circular dichroism measurements. The folding process depends highly on the detergent concentration and can be divided into an ultrafast phase (k > 1000 s(-1)), a fast phase (200-800 s(-1)), and a slow phase (25-70 s(-1)). The slow phase is absent in the W100F mutant. Secondary structure analysis and comparision with closely related proteins led to a new model of the structure of OEP16, suggesting that the protein is, in contrast to most other outer membrane proteins studied so far, purely alpha-helical, consisting of four transmembrane helices. Trp-77 is located in helix II, whereas the Trp-100 is located in the loop between helices II and III, close to the interface to helix III. We suggest that the first, very fast process corresponds to the formation of the helices, whereas the insertion of the helices into the detergent micelle and the correct folding of the II-III loop may be the later, rate-limiting steps of the folding process.

Amino Acid Sequence↗
PubMed2003

Membrane protein folding: beyond the two stage model.

The folding of alpha-helical membrane proteins has previously been described using the two stage model, in which the membrane insertion of independently stable alpha-helices is followed by their mutual interactions within the membrane to give higher order folding and oligomerization. Given recent advances in our understanding of membrane protein structure it has become apparent that in some cases the model may not fully represent the folding process. Here we present a three stage model which gives considerations to ligand binding, folding of extramembranous loops, insertion of peripheral domains and the formation of quaternary structure.

Aquaporins↗