Carboxyphosphonoenolpyruvate phosphonomutase, a novel enzyme catalyzing C-P bond formation.

An enzyme catalyzing the formation of an unusual C-P bond that is involved in the biosynthesis of the antibiotic bialaphos (BA) was isolated from the cell extract of a mutant (NP71) of Streptomyces hygroscopicus SF1293. This enzyme, carboxyphosphonoenolpyruvate (CPEP) phosphonomutase, was first identified as a protein lacking in a mutant (NP213) defective in one of the steps in the pathway to BA. The first 30 residues of the amino terminus of this protein were identical to those predicted by the nucleotide sequence of the gene that restored BA production to NP213. The substrate of the enzyme, a P-carboxylated derivative of phosphoenolpyruvate named CPEP, was also isolated from the broth filtrate of NP213 as a new biosynthetic intermediate of BA. CPEP phosphonomutase catalyzes the rearrangement of the carboxyphosphono group of CPEP to form the C-P bond of phosphinopyruvate.     

Measurement of intracellular Na in the rat salivary gland: a 23Na-NMR study using double quantum filtering

23Na in the prefused rat mandibular salivary gland was measured by spin-echo double quantum filter 23Na-NMR spectroscopy at 8.45 T. Resonances due to the intracellular 23Na and the interstitial 23Na were observed in the perfused gland at 25 degrees C. The resonance due to intracellular 23Na consisted of two Lorentzian signals stemming from the [1/2 mean value of -1/2[ coherence (sharp resonance) and the [-1/2 mean value of -3/2[ and [3/2 mean value of 1/2[ coherences (broad resonance). The transverse relaxation rate constant corresponding to the [1/2 mean value of -1/2[ coherence was 95 +/- 4 s-1 and that corresponding to the [-1/2 mean value of -3/2[ and [3/2 mean value of 1/2[ coherences was 1360 +/- 75 s-1 (mean +/- S.E., n = 5). The resonance due to the interstitial 32Na had longer relaxation rate constants, and disappeared upon administration of dysprosium triethylenetetramine-N,N',N",N",N"'-hexaacetic acid.     

Saccharomyces cerevisiae spheroplasts are sensitive to the action of diphtheria toxin.

Diphtheria toxin kills spheroplasts of Saccharomyces cerevisiae but not the intact yeast cells. After 2 h of exposure to ca. 10(-7) M toxin, less than 1% of spheroplasts were able to regenerate into intact cells. The same high levels of toxin inhibited the rate of protein synthesis by more than 90% within 1 h, whereas RNA and DNA synthesis were not inhibited until 4 h or exposure. Both killing and protein synthesis inhibition were dependent on toxin concentration. The nature of the toxin-cell interaction was also studied by using fragments of intact toxin and mutant toxin proteins. Neither toxin fragment A nor CRM45 nor CRM197 affected spheroplasts, but CRM197 and ATP prevented the inhibitory action of intact toxin. These results suggest that toxin acts on S. cerevisiae spheroplasts in much the same manner as it acts on sensitive mammalian cells.     

Growth of mouse plasmacytoma cells in serum-free, hormone-supplemented medium: procedure for the determination of hormone and growth factor requirements for cell growth

The procedure of analyzing hormone and growth factor requirements for the growth of MPC-11 cells and of developing a serum-free medium for this cell line has been described. In this medium, MPC-11 cells grow as fast as in serum-supplemented medium, up to 50 generation. MPC-11 cells grown in serum-supplemented medium secrete IgG_2b and K light chain into the medium as they do in serum-containing medium.     

Hydrocephalus in suckling rats infected intracerebrally with mouse hepatitis virus, MHV-A59

After intracerebral inoculation of mouse hepatitis virus, MHV-A59 strain, into 3- to 5-day-old Wistar rats, some survivors at 14 days postinoculation (p.i.) were found to lack the cerebral cortex and to have an accumulation of considerable amount of cerebrospinal fluid. The virus titer in the brain increased exponentially after inoculation, reaching a maximum 4 to 6 days p.i. when immunofluorescence revealed virus-specific antigen within neurons in the cerebral cortex. A small amount of infectious virus was also detectable 14 days p.i. when the cerebral anomaly was evident. This brain malformation causing hydrocephalus was due to cerebral damage by viral infection.     

Studies on the nuclear binding of steroid hormone-receptor complex; binding of liver and thymus dexamethasone-receptor complex and prostate dihydrotestosterone-receptor complex to nuclei from various tissues.

To examine the binding specificity of steroid hormone-cytoplasmic receptor complexes to nuclei, binding of 3H-dexamethasone (Dex)-liver, 3H-Dex-thymus and 3H-dihydrotestosterone (DHT)-prostate receptor complexes to nuclei from liver, prostate, thymus, spleen and kidney was studied. It was observed that a significant amount of steroid-receptor complexes was bound to any nuclei used in the present study and the extent of the binding of receptor complexes to nuclei from homologous tissues was not always greater than that to nuclei from heterogenous tissues. However, a significant portion of the 3H-Dex-liver and 3H-DHT-prostate receptor complexes was not absorbed by nuclei from kidney, spleem, and thymus, and the unabsorbed complexes were efficiently bound to liver and prostate nuclei. The results obtained indicate that two types of receptor complex with regard to nuclear binding were present in cytosols of liver and prostate; one binds to nuclei from kidney, spleen, thymus, liver and prostate and the other does not bind to nuclei from kidney, spleen and thymus but does bind to nuclei of liver and prostate. The latter type of receptor complex was not observed in the cytosol from the thymus.     

The role of polyamines in the regulation of AMP deaminase isozymes

The differential effects of polyamines on the activity of AMP deaminase isozyme A (from rat muscle) and isozyme B (from rat liver) are reported. Polyamines activate isozyme B but inhibit isozyme A.     

X-ray-induced recombination during oogenesis in the silkworm (Bombyx mori L.)

Summary The physical induction of recombinational events has been studied in the female silkworm (Bombyx mori), in which crossing-over does not normally occur. Female silkworms heterozygous in the trans type of two egg-color genes,pe (V-0.0) andre (V-31.7), received a single dose of X-rays (1000 R) at various developmental stages. Then they were crossed to marked males homozygous for both genes. The results indicated that X-rays increase the occurrence of recombinational events in silkworm females from first instar larvae to late stage pupae. The spontaneous frequency of exchange type recombinants in the control series was 2.5 x 10^–5, while after irradiation the frequency of these recombinants was up to 38.8 x^10–5. The sensitive stage to X-ray-induced recombinational events was late stage larvae from fourth to fifth instar. Exchange (cross-over) type recombinants were about three times more frequent than interchange types among the 122 recombinants recovered. The biological significance of the present finding is discussed.     

The physiological significance of the xanthurenic acid-insulin comples.

The xanthurenic acid-insulin complex was found to have similar immunological properties to native Zn-insulin. This complex showed less hormonal activity on glucose metabolism in adipose tissue than native An-insulin, but its activity was increased by addition of Zn2+ ions.