ATPase activity of SopA, a protein essential for active partitioning of F plasmid

Summary The SopA, B, C genes of the F plasmid play an essential role in plasmid partitioning during cell division in Escherichia coli. In this paper, the products of the sopA and sopB genes were isolated and their biochemical activities studied. [-³²P]ATP was cross-linked to the SopA protein by UV irradiation; this cross-linking was observed only in the presence of magnesium ion, and was competitively inhibited in the presence of non-radioactive ATP, ADP and dATP, but not other NTPs or dNTPs. In contrast, no ATP binding activity was detected for the SopB protein. The SopA protein showed a modest magnesium ion-dependent ATPase activity and this activity was stimulated in the presence of DNA. The ATPase activity in the presence of DNA was further stimulated by addition of the SopB protein. However, the SopB protein alone failed to stimulate the ATPase activity.     

Effects of mutagens on the clonal lifespan of Paramecium tetraurelia.

There has been interest in the phenomenon that a cell cannot undergo unlimited reproduction under adequate conditions and undergoes senescence. In holotrichous ciliates, Paramecium has a limit of vegetative reproduction without sexual reproduction but Tetrahymena does not always have a limited lifespan. Comparing the two species would increase our knowledge of the mechanism of cellular clonal aging. We previously showed that mutations induced by X-rays shorten clonal lifespan. In this study, we examined whether mutagens shorten the clonal lifespan of Paramecium tetraurelia. P. tetraurelia was exposed to the alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), 0.045 mg/ml, for 30 min. The animal was exposed to MNNG 6 times in total while young (under 80 divisions from the start of a clonal life cycle) or 4 times during the senescent stage. MNNG shortened the clonal lifespan as expressed by the decrease in fission number from 186 +/- 55 (4 cell lines) to 136 +/- 21 (6 cell lines) with the first two treatments but with further exposures the lifespan increased to 182 +/- 15 (5 cell lines). MNNG had no effect when administered at the older age. Exposure of P. tetraurelia to 4-nitroquinoline-N-oxide at 0.021 mg/ml twice for 12 and 15 min at the younger age reduced the mean clonal lifespan from 143 +/- 28 to 125 +/- 21 and the maximum lifespan from 263 +/- 33 to 175 +/- 25.     

Oleanane glycosides from Glycyrrhiza yunnanensis roots.

From the roots of Glycyrrhiza yunnanensis, collected in Yunnan, China, six new oleanane-type triterpene glycosides named yunganosides A1, B1, C1, D1, E2 and F2 were isolated together with hypaphorine. The structures of these glycosides were established by spectroscopic and chemical means.     

Identification and Characterization of the ictA/ndhL Gene Product Essential to Inorganic Carbon Transport of Synechocystis PCC6803

The ictA gene, renamed ndhL in this paper, essential to inorganic carbon transport of Synechocystis PCC6803, was expressed in Eschericia coli as a fusion protein with glutathione S-transferase. An antibody was raised against this fusion protein. Western analysis of the thylakoid membrane of wild-type (WT) Synechocystis revealed that a protein with an apparent molecular mass of 6.7 kilodaltons cross-reacted with this antibody. No immunoreactive protein was present in the thylakoid membranes of the Synechocystis mutants, RKb and M9, which have defects in the ictA/ndhL gene, or in the cytoplasmic membranes of the WT and mutant cells. Thus, the protein reacted with the antibody is the ictA gene product (IctA) and is localized in the thylakoid membrane of WT cells. IctA was absent in the thylakoid membranes of the M55 mutant, in which the ndhB gene is inactivated, and was poorly immunostained in the membranes of the mutants (M-ndhC and M-ndhK) constructed by inactivating the ndhC and ndhK genes of WT Synechocystis, respectively. The carbon dioxide uptake activity was nearly zero in M-ndhK and was about 40% of the activity of WT cells in M-ndhC. The RKb, M-ndhC, and M-ndhK mutants were unable to grow or grew very slowly under photoheterotrophic conditions. These results indicated that NADH dehydrogenase is essential to inorganic carbon transport and photoheterotrophic growth of Synechocystis and that IctA is one of the subunits of this enzyme.     

ATP-dependent strontium uptake by basolateral membrane vesicles from rat renal cortex in the absence or presence of calcium

ATP-dependent Sr²⁺ transport was examined in vitro using basolateral membrane (BLM) vesicles isolated from rat renal cortex to clarify the discrimination mechanisms between strontium (Sr) and calcium (Ca) in renal tubules during reabsorption. ATP-dependent Sr²⁺ uptake and Ca²⁺ uptake were observed in renal BLM vesicles and were inhibited by vanadate. Hill plots indicate similar kinetic behavior for Ca²⁺ and Sr²⁺ uptake. The apparentK _m andV _max of ATP-dependent Sr²⁺ uptake were both higher than those for Ca²⁺ uptake. ATP-dependent Sr²⁺ uptake by BLM vesicles diminished in the presence of 0.1 μM Ca²⁺ and was more markedly inhibited by 1 μM Ca²⁺. Hill plots of Sr²⁺ uptake data with and without 0.1 μM Ca²⁺ showed that the cooperative behavior of Sr²⁺ uptake was not changed by Ca²⁺. In the presence of 0.1 μM Ca²⁺, the affinity of the transport system for Sr²⁺ and the velocity of Sr²⁺ uptake in the BLM were both decreased. However, the rate of Ca²⁺ uptake was not diminished by Sr²⁺ concentrations of <1.6 μM. These results suggest that Ca²⁺ is preferentially transported in the renal cortex BLM when Ca²⁺ and Sr²⁺ are present at the same time.     

Effect of addition of polyethyleneimine on thermal stability and activity of glucose dehydrogenase

When polyethyleneimine (PEI), a water-soluble cationic polymer, was added to solutions of glucose dehydrogenase (GDH) from Bacillus megaterium IWG3 at a molar ratio of PEI to GDH greater than 10, the thermal stability of GDH markedly increased. By addition of PEI, the rate of GDH-catalysed oxidation of -d-glucose increased in a low concentration range of NAD⁺ and NADP⁺ and the Michaelis constants and inhibition constants for both NAD⁺ and NADP⁺ decreased. These results suggested that negatively charged GDH interacts with cationic water-soluble polymers to form conjugates by electrostatic attraction, and also that negatively charged coenzymes are adsorbed by the polymers, resulting in enrichment of the coenzymes in the vicinity of GDH. Addition of PEI was also found to be effective for preventing the denaturation of GDH by acrylamide.Correspondence to: M. Teramoto     

Microbial asymmetric hydrolysis of N-acetyl-1-methyl-3-phenylpropylamine to optically active 1-methyl-3-phenylpropylamine

Summary The asymmetric hydrolysis of N-acetyl-1-methyl-3-phenypropylamine (MPAc) by microorganisms was investigated. Various bacteria belonging to the genera Bacillus, Agrobacterium, Corynebacterium, Arthrobacter, Brevibacterium, Cellulomonas, Acinetobacter, Nocardia and Rhodococcus showed this hydrolysing activity and yielded (S)-1-methyl-3-phenylpropylamine (MPPA). Using washed cells of N. erythropolis IAM 1440, 15.1 mg/ml of (S)-MPPA was formed, with a 38.8% conversion yield and high stereoselectivity (97.9% enantiomeric excess), in an organic solvent-water diphase system. The same (S)-amine and (S)-1-phenylethylamine were also produced in good yields from the valeryl and isovaleryl derivatives of MPPA, and N-acetyl-1-phenylethylamine, respectively.     

Memory impairment and morphological changes in rats induced by active fragment of anti-nerve growth factor-antibody

Treatment of rats with a specific Fab' fragment of anti-nerve growth factor (NGF)-antibody (anti-NGF, 12, 120 and 400 micrograms/4 weeks, i.c.v.) impaired their learning ability. The distance of swimming of anti-NGF-treated rats in a water maze was shortened more slowly by training than that of control rats. Anti-NGF treatment altered the staining of nuclei of cells in the hippocampus, parietal cortex and dentate gyrus with hematoxylin. It is suggested that the anti-NGF-induced amnesia could be due to change in nuclear morphology.