Mutagenic action of phaseolinone, a mycotoxin isolated from Macrophomina phaseolina

Phaseolinone was mutagenic to excision-repair-deficient strains of Escherichia coli WP2 and also to Salmonella typhimurium TA 100. The repair test was indicative of covalent binding of the toxin to DNA. The side-chain epoxide and the hydroxy groups of the molecule were found to be essential for mutagenic activity.     

Effect of malathion and radiation separately and jointly upon rat enzymes in vivo.

The effect of malathion (50 mg/kg) and radiation (900R) separately and jointly upon phosphatases and succinic dehydrogenase has been studied in female albino rats. Malathion and radiation when given separately, at the dose levels used in this study, appear to have no effect on acid and alkaline phosphatase of kidney, heart and brain. In preirradiated rats given malathion a significant decrease in phosphatases was observed in kidney and brain tissue after as little as 2 h and the values persisted for up to 24 h. No significant change was observed in heart tissue. At the dose level of 50 mg/kg of malathion, no significant change in succinic dehydrogenase was observed; however, radiation caused a significant increase in succinic dehydrogenase of brain and kidney tissue. In preirradiated rats given malathion the effect appeared to be enhanced in time to a certain degree. One could therefore speculate that simple non-specific stress caused by malathion adds to a similar effort of radiation by reducing phosphatases and enhancing the succinic dehydrogenase enzyme.     

Two new sterols from Physalis franchetii fruit

Two new steroids physanol A, 3β-benzoyloxy-6-oxo-stigmast-7,20-diene-11α-ol and physanol B, 3β-benzoyloxy-6-oxo-stigmast-7-ene-11α-ol have been isolated from the fruit of Physalis franchetti.     

Characterization of the phosphorylation sites and the surrounding amino acid sequences of the p21 transforming proteins coded for by the Harvey and Kirsten strains of murine sarcoma viruses

The transforming protein coded for by the onc gene (v-rasHa) of Harvey murine sarcoma virus (Ha-MuSV) is the 21,000-dalton protein (p21) which is the immediate agent responsible for the virus-induced malignant transformation of normal cells. The p21 proteins of Ha-MuSV and the closely related Kirsten murine sarcoma virus are heavily phosphorylated in vivo. In the partially purified Ha-MuSV p21, the protein shows a guanine nucleotide-binding activity and, in addition, a very unique autophosphorylating activity at a threonine residue using as phosphoryl donor GTP but not ATP. In the present study, we compared the tryptic peptide maps of the Ha-MuSV p21 phosphorylated in vivo and in vitro. The results show that the major phosphorylation site is identical. Since the GTP-specific phosphorylation is very unique and distinct from all other known protein kinases, the present observation suggests that the in vitro enzymatic activity is responsible for the p21 phosphorylation in vivo. We have analyzed the amino acid sequence surrounding the major phosphorylation site of the Ha-MuSV p21 by automated Edman degradations of the tryptic phosphopeptides. Threonine residue 59 from the initiator methionine residue 1 of the p21 protein is the phosphorylated amino acid residue, and the surrounding amino acid sequence is NH2...-Thr-Cys-Leu-Leu-Asp-Ile-Leu-Asp-Thr-Thr(P)-Gly-Gln-Glu-Glu-Tyr-...COOH. The p21 proteins of both the Ha-MuSV and the closely related Kirsten murine sarcoma virus share the same phosphopeptide. The amino acid sequence of the phosphorylation site is distinct from all other known protein kinases.