Effect of streptomycin on the stoichiometry of GTP hydrolysis in a poly(U)-dependent cell-free translation system

The technique of Sepharose-bound template translation has been used to estimate the stoichiometry of GTP hydrolysis during peptide elongation in the presence of streptomycin. The presence of streptomycin has been shown to have no great effect on the elongation rate and the stoichiometry of GTP hydrolysis during codon-specific peptide elongation in the poly(U)-directed translation system: the molar ratio of hydrolysed GTP to incorporated phenylalanine was about 2. At the same time streptomycin exerted a significant effect during misreading when a ribosome-bound peptide in the poly(U)-programmed system was elongated by leucine or isoleucine residues: the miselongation was stimulated and hence the ratio of hydrolysed GTP per peptide bond was strongly reduced, as compared with the excessive GTP hydrolysis which is characteristic of the misreading system in the absence of streptomycin [(1984) FEBS Lett. 178, 283-287]. The conclusion has been made that streptomycin blocks the stage of correction ('proof-reading') following GTP hydrolysis during EF-Tu-dependent aminoacyl-tRNA binding.     

Factor-free and one-factor-promoted poly(U,C)-dependent synthesis of polypeptides in cell-free systems from Escherichia coli

α-Tropomyosin from rat cardiac muscle was shown by two-dimensional gel electrophoresis to become phosphorylated when tissue slices were incubated in Eagle's medium supplemented with ³²P_i. In the adult rat and mouse heart the level of phosphorylation was ～30%, but the level was much higher in the foetal heart (60–70%). A similar developmental trend was observed in skeletal muscle from the rat and mouse, where phosphorylated forms of both α- and β-tropomyosins were observed. When rat cardiac cells were grown in tissue culture in the presence of ³²P_i, radioactivity was incorporated into the region of the gel containing tropomyosin.     

Isolation and immunochemical study of monomer and dimer forms of IgA human globulins]

Monomer and dimer of myeloma IgA human globulins are isolated by means of electrophoresis, ionic exchange chromatography, gel filtration and immunoadsorbtion. They are shown to be homogenous (using analytical ultracentrifugation and immunochemical analysis) and to differ in their antigenic specificity. Dimeric form of IgA has additional antigenic determinants, which depend on the intactness of a polymer structure and which are destroyed after protein dissociation into subunits in the presence of beta-mercaptoethanol. Reconstructed polymers are polydispersed subunit aggregates, they do not have polymeric determinants inherent to native polymers.     

Participation of the hippocampus in regulating a pathologic inactive motor reaction in dogs

A local pathological inert motor reaction, involving a forced flexion of the forepaw, was formed after simultaneous stimulation with NaCl solution of a part of the tongue brought out to the cheek and electrical stimulation of the forepaw. The reaction decreased (by 70 to 80%) after electrical stimulation of the dorsal hippocampus (beyond CA3). At the same time the animal's emotional stress diminished, as evidenced by the reduced heart rate and a reduced theta-rhythm in the hippocampus.     

Special effects of a complex probiotic containing cellulolytic bacteria Cellulomonas on actively growing rabbits

It was shown that the association of probiotic bacteria of the genuses Bacillus and Cellulomonas form biolayers on the surface of beet marc particles. The positive effect of a fodder additive that contained the biolayer on the basis of a phytomatrix on the growth and development of young rabbits was shown. Feeding of animals with a mixed fodder that contained 0.1% preparation resulted in stimulation of digestion of all components of the food. Among other components of the mixed fodder, cellulose was digested most effectively. An increase in the biomass of symbiotic bacteria and enzymatic activity in the blindgut chymus was also observed. The positive nitrogen balance demonstrated an increase in the nitrogen content in animals and a decrease of its losses with excretion. The mechanism of response of the rabbit’s organism to introduction of the complex probiotic preparation into the digestive tract is discussed.     

European checkerspots (Melitaeini: Lepidoptera,Nymphalidae) are not aposematic – the point of view of great tits (Parus major)

相似文献   

Characterization of the mitochondrial genome of the MAX1 type of cytoplasmic male-sterile sunflower

Background

More than 70 cytoplasmic male sterility (CMS) types have been identified in Helianthus, but only for less than half of them, research of mitochondrial organization has been conducted. Moreover, complete mitochondrion sequences have only been published for two CMS sources – PET1 and PET2. It has been demonstrated that other sunflower CMS sources like MAX1, significantly differ from the PET1 and PET2 types. However, possible molecular causes for the CMS induction by MAX1 have not yet been proposed. In the present study, we have investigated structural changes in the mitochondrial genome of HA89 (MAX1) CMS sunflower line in comparison to the fertile mitochondrial genome.

Results

Eight significant major reorganization events have been determined in HA89 (MAX1) mtDNA: one 110 kb inverted region, four deletions of 439 bp, 978 bp, 3183 bp and 14,296 bp, respectively, and three insertions of 1999 bp, 5272 bp and 6583 bp. The rearrangements have led to functional changes in the mitochondrial genome of HA89 (MAX1) resulting in the complete elimination of orf777 and the appearance of new ORFs - orf306, orf480, orf645 and orf1287. Aligning the mtDNA of the CMS sources PET1 and PET2 with MAX1 we found some common reorganization features in their mitochondrial genome sequences.

Conclusion

The new open reading frame orf1287, representing a chimeric atp6 gene, may play a key role in MAX1 CMS phenotype formation in sunflower, while the contribution of other mitochondrial reorganizations seems to appear negligible for the CMS development.