Molecular architecture of E. coli purine nucleoside phosphorylase studied by analytical ultracentrifugation and CD spectroscopy.

Purine nucleoside phosphorylase (PNP) is a key enzyme of the nucleoside salvage pathway and is characterized by complex kinetics. It was suggested that this is due to coexistence of various oligomeric forms that differ in specific activity. In this work, the molecular architecture of Escherichia coli PNP in solution was studied by analytical ultracentrifugation and CD spectroscopy.

Domain stability in the AAA+ ATPase ClpB from Escherichia coli.

ClpB is a heat-shock protein that reactivates aggregated proteins in cooperation with the DnaK chaperone system. ClpB belongs to the family of AAA+ ATPases and forms ring-shaped oligomers: heptamers in the absence of nucleotides and hexamers in the presence of nucleotides. We investigated the thermodynamic stability of ClpB in its monomeric and oligomeric forms.

Nucleotide-induced switch in oligomerization of the AAA+ ATPase ClpB.

ClpB is a member of the bacterial protein-disaggregating chaperone machinery and belongs to the AAA(+) superfamily of ATPases associated with various cellular activities. The mechanism of ClpB-assisted reactivation of strongly aggregated proteins is unknown and the oligomeric state of ClpB has been under discussion. Sedimentation equilibrium and sedimentation velocity show that, under physiological ionic strength in the absence of nucleotides, ClpB from Escherichia coli undergoes reversible self-association that involves protein concentration-dependent populations of monomers, heptamers, and intermediate-size oligomers.

Structure and function of the middle domain of ClpB from Escherichia coli.

ClpB belongs to the Hsp100/Clp ATPase family. Whereas a homologue of ClpB, ClpA, interacts with and stimulates the peptidase ClpP, ClpB does not associate with peptidases and instead cooperates with DnaK/DnaJ/GrpE in an efficient reactivation of severely aggregated proteins. The major difference between ClpA and ClpB is located in the middle sequence region (MD) that is much longer in ClpB than in ClpA and contains several segments of coiled-coil-like heptad repeats.

Conserved amino acid residues within the amino-terminal domain of ClpB are essential for the chaperone activity.

ClpB from Escherichia coli is a member of a protein-disaggregating multi-chaperone system that also includes DnaK, DnaJ, and GrpE. The sequence of ClpB contains two ATP-binding domains that are enclosed between the amino-terminal and carboxyl-terminal regions. The N-terminal sequence region does not contain known functional sequence motifs.

[The effect of low intensity electromagnetic irradiation on hydration of DNA film].

By using the IR-spectroscopy it has been shown that electromagnetic radiation (frequency 8.15-10.0 GHz, energy flux density 5 microWt/cm2) reduces the rate of water desorption from DNA films.

Hyperosmotic hemolysis and antihemolytic activity of the saponin fraction and triterpene glycosides from Panax ginseng C. A. Meyer.

A saponin fraction and triterpene glycosides Rb1, Rb2 and Rg1 from Panax ginseng C. A. Meyer (saponins) were shown to inhibit the hyperosmotic hemolysis of erythrocytes.

The effect of oxidative stress on structural transitions of human erythrocyte ghost membranes.

Differential scanning microcalorimetry was used to study the effect of oxidative stress induced by cumene hydroperoxide (CHP) and Fe2+ on structural transitions of membranes of human erythrocyte ghosts. The CHP homolysis was shown to cause: (a) reduction of the intensity of all structural transitions with the disappearance of B1- and D-transitions; (b) decrease in the enthalpy of oxidized membrane denaturation; (c) negative slope of thermograms; (d) anomalous growth of heat absorption by membranes above 72 degreesC. All these changes occurred until the ratio Fe2+/CHP/membranes<0.

Effects of triterpenoid glycosides of the dammaran series and their aglycons on phase transitions of dipalmitoylphosphatidylcholine.

The effects of triterpenoid glycosides from Korean red ginseng Panax C.A. Meyer and their aglycons on the phase transitions of model DPPC membranes were studied by microcalorimetry.

[Effect of ginseng ginsenosides on phase transitions of dipalmitoylphosphatidylcholine membranes].

The influence of dammaran triterpene glycosides (ginsenosides Rb1 and Rg1) from Panax Ginseng C.A. Meyer and their aglycones on the phase transfers of multilayer vesicles of dipalmitoylphosphatidyl choline was studied.