Orthophenylphenol (OPP), a widely used fungicide, induced ouabain-resistant (OuaR) mutants in a ultraviolet (UV)-sensitive human RSa cell strain and the frequencies increased in a dose-related fashion. OPP was a more potent mutagen than UV at doses related to equal survival. These results suggest that OPP has a mutagenic activity and that further experiments on this chemical are warranted.

Biphenyl Compounds↗

PubMedDate not supplied

Tubulin and high molecular weight microtubule-associated proteins as endogenous substrates for protein carboxymethyltransferase in brain.

The endogenous substrate for protein carboxymethyltransferase in brain was examined. Several polypeptides were methylated when brain slices were incubated with L-methionine or when subcellular fractions of brain, such as the cytosolic fraction, were incubated with S-adenosyl L-methionine. Two methyl-accepting proteins in the cytoplasm were identified as tubulin and high molecular weight microtubule-associated proteins (300 kDa), which are components of microtubules. Tubulin behaved as a 43 kDa protein in acidic polyacrylamide gel electrophoresis, but as a 55 kDa protein in SDS-polyacrylamide gel electrophoresis. The methyl moiety transferred to these proteins from L-methionine was labile at alkaline pH. The high molecular weight microtubule-associated proteins showed higher methyl-accepting activity than tubulin or ovalbumin, which was used as a standard substrate: about 20 mmol of high molecular weight microtubule-associated proteins, 2 mmol of tubulin and 10 mmol of ovalbumin were methylated per mol of each protein in 30 min under the experimental conditions used.

Animals↗