ISSN:
1471-4159
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
Abstract: Protein carboxylmethyltransferase has been proposed to play a role in the regulation of neuroblastoma differentiation (Kloog et al., 1983). When we investigated this hypothesis further, different results for methyl ester formation were obtained when measured in acid-precipitated proteins and in proteins separated by acidic polyacrylamide gel electrophoresis, following the incubation of intact neuroblastoma cells with [3H]methionine. These unexpected findings led to the development of a modified assay using S-[3H]-adenosylmethionine as the radiolabeled precursor for quan-titating carboxyl methylation in intact cells. Data obtained from either acid-precipitated proteins or those separated on an electrophoresis gel following S-[3H]adenosylmethionine incubation directly correlated with data obtained from proteins separated by electrophoresis following [3H]methionine incubation. Using each of the three methods, an approxi-mately twofold increase in the carboxyl methylation of cellular proteins was detected in neuroblastoma cells differentiated by reducing the serum concentration from 10 to 0.5%, but not in those cells differentiated with either 5 mMhexa-methylene bisacetamide or 2% dimethyl sulfoxide. The finding that all detectable methyl acceptor proteins are increasingly methylated following 0.5% serum treatment and that this modification is substoichiometric suggests that protein carboxyl methylation is not an essential component of the differentiation process in neuroblastoma cells.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1471-4159.1989.tb07409.x
