Proteomic and functional analysis of the mitotic Drosophila centrosome

Regulation of centrosome structure, duplication and segregation is integrated into cellular pathways that control cell cycle progression and growth. As part of these pathways, numerous proteins with well‐established non‐centrosomal localization and function associate with the centrosome to fulfill regulatory functions. In turn, classical centrosomal components take up functional and structural roles as part of other cellular organelles and compartments. Thus, although a comprehensive inventory of centrosome components is missing, emerging evidence indicates that its molecular composition reflects the complexity of its functions. We analysed the Drosophila embryonic centrosomal proteome using immunoisolation in combination with mass spectrometry. The 251 identified components were functionally characterized by RNA interference. Among those, a core group of 11 proteins was critical for centrosome structure maintenance. Depletion of any of these proteins in Drosophila SL2 cells resulted in centrosome disintegration, revealing a molecular dependency of centrosome structure on components of the protein translation machinery, actin‐ and RNA‐binding proteins. In total, we assigned novel centrosome‐related functions to 24 proteins and confirmed 13 of these in human cells.     

Maintaining high anaerobic succinic acid productivity by product removal

During dual-phase fermentations using Escherichia coli engineered for succinic acid production, the productivity and viable cell concentration decrease as the concentration of succinic acid increases. The effects of succinic acid on the fermentation kinetics, yield, and cell viability were investigated by resuspending cells in fresh media after selected fermentation times. The cellular succinic acid productivity could be restored, but cell viability continuously decreased throughout the fermentations by up to 80% and subsequently the volumetric productivity was reduced. Omitting complex nutrients in the resuspension media had no significant effect on cellular succinate productivity and yield, although the viable cell concentration and thus the volumetric productivity was reduced by approximately 20%. By resuspending the cells, the amount of succinate produced during a 100-h fermentation was increased by more than 60%. The results demonstrate that by product removal succinic acid productivity can be maintained at high levels for extended periods of time.     

Effect of of distamycin A on histone H1 methylation, extraction and formation of UV-inducible crosslinks with DNA in the interphase rat liver nucleus

Incubation in vitro of rat liver nuclei in the presence of S-adenosyl[methyl-(3)H]methionine ([(3)H] SAM) leads to incorporation of the radioactive label not only into core-histones H3 and H4, but also into linker histone H1. Addition of distamycine A to the incubation medium stimulates label incorporation into histone H1 ~ in 6 times and into histone H3 ~ in 2 times. The presence of distamycine facilitates histone H1 extraction by polyglutamic acid (poly(Glu)) and decreases of UV-induced DNA-histone cross-links formation. These effects give evidence of weakening of H1-chromatin interaction by distamycin to be results of histone H1 position change relative to nucleosome and(or) disturbance of histones H1-H3 interactions so as these histones are exposed to additional methylation.     

Redox potential of the Rieske iron-sulfur protein: Quantum-chemical and electrostatic study

Quantum-chemical study of structures, energies, and effective partial charge distribution for several models of the Rieske protein redox center is performed in terms of the B3LYP density functional method in combination with the broken symmetry approach using three different atomic basis sets. The structure of the redox complex optimized in vacuum differs markedly from that inside the protein. This means that the protein matrix imposes some stress on the active site resulting in distortion of its structure. The redox potentials calculated for the real active site structure are in a substantially better agreement with the experiment than those calculated for the idealized structure. This shows an important role of the active site distortion in tuning its redox potential. The reference absolute electrode potential of the standard hydrogen electrode is used that accounts for the correction caused by the water surface potential. Electrostatic calculations are performed in the framework of the polarizable solute model. Two dielectric permittivities of the protein are employed: the optical permittivity for calculation of the intraprotein electric field, and the static permittivity for calculation of the dielectric response energy. Only this approach results in a reasonable agreement of the calculated and experimental redox potentials.     

Larvicidal activity of crystal-forming strains of <Emphasis Type="Italic">Brevibacillus laterosporus</Emphasis>

The optimum conditions for growth, sporulation, and crystal-formation in four isolated crystal-forming strains of Bacillus laterosporus were determined. It was shown that culture broth and pellets of bacterial culture liquid possess larvicidal activity against larvae of mosquitoes A. stephensi and A. aegypti. The protein nature of crystal was shown. Crystals are monocomponent containing a protein with MM of 68 or 130 kDa. Purified protein crystals demonstrated larvicidal activity. Specific larvicidal activity of crystals of various strains essentially differed. High larvicidal activity of B. laterosporus strains allows for them to be recommended as producers of antimosquito biological preparations.     

Polymer Partitioning and Ion Selectivity Suggest Asymmetrical Shape for the Membrane Pore Formed by Epsilon Toxin

Using poly-(ethylene glycol)s of different molecular weights, we probe the channels formed in planar lipid bilayers by epsilon toxin secreted by the anaerobic bacterium Clostridium perfringens. We find that the pore is highly asymmetric. The cutoff size of polymers entering the pore through its opening from the cis side, the side of toxin addition, is ∼500 Da, whereas the cutoff size for the polymers entering from the trans side is ∼2300 Da. Comparing these characteristic molecular weights with those reported earlier for OmpF porin and the α-Hemolysin channel, we estimate the radii of cis and trans openings as 0.4 nm and 1.0 nm, respectively. The simplest geometry corresponding to these findings is that of a truncated cone. The asymmetry of the pore is also confirmed by measurements of the reversal potential at oppositely directed salt gradients. The moderate anionic selectivity of the channel is salted-out more efficiently when the salt concentration is higher at the trans side of the pore.     

A new gnetalean pollen genus <Emphasis Type="Italic">Chomsiipites</Emphasis> from cretaceous deposits of the eastern mediterranean

Four species of a new genus, Chomsiipites—Ch. libanicus sp. nov., Ch. pyriformis sp. nov., Ch. dzyubae sp. nov., and Ch. zaklinskaiae (Azèma et Boltenhagen) comb. nov.—are described from the Albian-Cenomanian of western part of Central Lebanon, Eastern Caspian Region, Albian-Turonian of Gabon, and Albian-Senonian of Angola (Equatorial Africa).