The turnover of vimentin in Ehrlich ascites tumour cells

The turnover of vimentin and vimentin-derived peptides has been examined in logarithmically growing Ehrlich ascites tumour cells. Cells were pulse-labelled with [35S]methionine for 30 min and then chased for up to 60 h. It was found that the specific radioactivity of the main isoelectric variant of vimentin decreased to half the original value in 15.3 h which was close to the division time of the cells (16 h). The protein moiety of the phosphorylated variant of vimentin also turned over very slowly, in contrast to the turnover rate of the phosphate group itself which has a half-life of 1.4 h. The role of the intermediate filament-specific, Ca2+-activated proteinase has been considered in relationship to the slow turnover of vimentin.