ABSTRACT
Hepatitis B virus core antigen (HBc) with the insertion of four external domains of the influenza A M2 protein (HBc/4M2e) form virus-like particles whose structure was studied using a combination of molecular modeling and cryo-electron microscopy (cryo-EM). It was also shown that self-assembling of the particles occurs inside bacterial cells, but despite the big inner volume of the core shell particle, purified HBc/4M2e contain an insignificant amount of bacterial proteins. It was shown that a fragment of the M2e corresponding to 4M2e insertion is prone to formation of amyloid-like fibrils. However, as the part of the immunodominant loop, M2e insertion does not show a tendency to intermolecular interaction. A full-atomic HBc-4M2e model with the resolution of about 3 Š(3.13 Šfor particles of Т = 4 symmetry, 3.7 Šfor particles of Т = 3 symmetry) was obtained by molecular modeling methods based on cryo-EM data.
Subject(s)
Hepatitis B Core Antigens , Viral Matrix Proteins , Cryoelectron Microscopy , Hepatitis B Core Antigens/chemistry , Hepatitis B virus/chemistry , Models, Molecular , Viral Matrix Proteins/chemistryABSTRACT
Two influenza A nucleoprotein variants (wild-type: G102R; and mutant: G102R and E292G) were studied with regard to macro-molecular interactions in oligomeric form (24-mers). The E292G mutation has been previously shown to provide cold adaptation. Molecular dynamics simulations of these complexes and trajectory analysis showed that the most significant difference between the obtained models was distance between nucleoprotein complex strands. The isolated complexes of two ribonucleoprotein variants were characterized by transmission electron microscopy and differential scanning fluorimetry (DSF). Presence of the E292G substitution was shown by DSF to affect nucleoprotein complex melting temperature. In the filament interface peptide model, it was shown that the peptide corresponding in primary structure to the wild-type NP (SGYDFEREGYS) is prone to temperature-dependent self-association, unlike the peptide corresponding to E292G substitution (SGYDFGREGYS). It was also shown that the SGYDFEREGYS peptide is capable of interacting with a monomeric nucleoprotein (wild type); this interaction's equilibrium dissociation constant is five orders of magnitude lower than for the SGYDFGREGYS peptide. Using small-angle neutron scattering (SANS), the supramolecular structures of isolated complexes of these proteins were studied at temperatures of 15, 32, and 37 °C. SANS data show that the structures of the studied complexes at elevated temperature differ from the rod-like particle model and react differently to temperature changes. The data suggest that the mechanism behind cold adaptation with E292G is associated with a weakening of the interaction between strands of the ribonucleoprotein complex and, as a result, the appearance of inter-chain interface flexibility necessary for complex function at low temperature.Communicated by Ramaswamy H. Sarma.
Subject(s)
Influenza A virus , Influenza, Human , Adaptation, Physiological , Cold Temperature , Humans , Influenza A virus/genetics , Nucleoproteins/geneticsABSTRACT
Confocal micro-Raman spectroscopy was used to measure cross-section linescans of the cleaved edge of heterostructures involving a GaMnAs layer. The investigations revealed a shift of the TO mode in the compressed GaMnAs layer to high frequencies relative to the TO GaAs mode in the substrate and to low frequencies in the tensile GaMnAs layers. These results are in agreement with the different manifestations of the anomalous Hall effect in the GaMnAs layers, with either compressive or tensile strains. It is shown that Raman spectroscopy is an appropriate method for the investigation of cross-sectional semiconductor heterostructures whose total thickness is comparable to the size of the analyzing laser spot.
ABSTRACT
We performed immunohistochemical analysis of the expression of caspases 3, 9 and bcl-2 protein in rat brain at various terms after administration of LD50 of sodium thiopental. Expression of the specified apoptosis markers was found in the sensorimotor cortex and hippocampus (dentate gyrus and CA2 region).
Subject(s)
Brain/metabolism , Caspase 3/metabolism , Caspase 9/metabolism , Coma/metabolism , Proto-Oncogene Proteins c-bcl-2/metabolism , Animals , Apoptosis/physiology , Brain/enzymology , Dentate Gyrus/metabolism , Hippocampus/metabolism , Immunohistochemistry , Male , RatsABSTRACT
The review summarizes current concepts on role of several covalent posttranslation chromatin modifications in the process of memory formation in vertebrate and invertebrate animals. There is described a chain of intracellular events from activation of receptors and signal pathways to change of the functional state of genome.
Subject(s)
Chromatin/genetics , Epigenesis, Genetic , Memory, Long-Term/physiology , Animals , DNA Methylation/genetics , Histones/genetics , Humans , Learning/physiology , Mitogen-Activated Protein Kinase Kinases/genetics , Protein Processing, Post-TranslationalABSTRACT
A review. Works related to research into the neuroanatomical basis of associative learning in the honeybee (proboscis extension reflex) are summarized. Data on the brain organization of the honeybee are presented. The parallel neural pathways of conditioned and unconditioned stimuli are shown. Contribution of different brain structures and identified neurons (VUMmx1, PE1) in the formation of the proboscis extension reflex are discussed.
Subject(s)
Bees/anatomy & histology , Bees/physiology , Conditioning, Classical , Animals , Association Learning , Brain/anatomy & histology , Brain/physiology , Mushroom Bodies/anatomy & histology , Mushroom Bodies/physiology , Neural Pathways , Olfactory PathwaysABSTRACT
It is known that RecX is a negative regulator of RecA protein. We found that the mutant RecA D112R protein exhibits increased resistance to RecX protein comparatively to wild-type RecA protein in vitro and in vivo. Using molecular modeling we showed, that amino acid located in position 112 can not approach RecX closer than 25-28 angstroms. Thus, direct contact between amino acid and RecX is impossible. RecA D112R protein more actively competes with SSB protein for the binding sites on ssDNA and, therefore, differs from the wild-type RecA protein by dynamics of filamentation on ssDNA. On the other hand, after the replacement of ATP by dATP, the wild-type RecA protein, changing the dynamics of filamentation on ssDNA, also becomes more resistant to RecX. Based on these data it is concluded that the dynamics of filamentation has a great, if not dominant role in the stability of RecA filament to RecX relative to the role of RecA-RecX protein-protein interactions discussed earlier. We also propose an improved model of regulation of RecA by RecX protein, where RecA filament elongation along ssDNA is blocked by RecX protein on the ssDNA region, located outside the filament.
Subject(s)
Arginine/chemistry , Aspartic Acid/chemistry , Escherichia coli Proteins/chemistry , Rec A Recombinases/chemistry , Adenosine Triphosphate/chemistry , Amino Acid Substitution , Arginine/genetics , Aspartic Acid/genetics , DNA, Single-Stranded/chemistry , DNA-Binding Proteins/chemistry , Enzyme Stability , Escherichia coli/enzymology , Escherichia coli/genetics , Models, Molecular , Mutation , Protein Conformation , Rec A Recombinases/geneticsABSTRACT
Conformational flexibility of alpha-helices in glucoamylase of the fungus Aspergillus awamori was studied by molecular dynamics methods. Several amino acid substitutions (G127A, P128A, I136L, G137A, and G139A) optimizing intrinsic interactions in one of the alpha-helices (D) within the hydrophobic core of this protein were constructed and studied. It was found that these point mutations had different effects on the glucoamylase thermal inactivation constant. Unlike amino acid substitution P128A and substitutions G137A and A246C, I136L and G139A displayed a pronounced additive thermostabilizing effect.
