Vimentin-derived proteins : Differences between normal human fibroblasts and transformed human cells

Two-dimensional gel electrophoresis revealed a quantitative difference in a series of polypeptides ranging in MW from 45 000 to 51 000 and of lower isoelectric pH than vimentin, when comparing normal human fibroblasts with a virally transformed subline and with HeLa cells. Re-extraction of purified ³⁵S]vimentin with cold whole cell homogenates and peptide mapping showed that these polypeptides are derivatives of vimentin. They may be natural components of a normal fibroblast's architecture or they may arise from a pool of vimentin that is not structured within intermediate filaments at the time of extraction. Furthermore, we show that vimentin from the two transformed cell types is more resistant to proteolysis by whole cell homogenates than vimentin from normal fibroblasts. Structural alteration of vimentin may play an important role in the expression of transformation.