Two-dimensional electrophoresis of soluble and structure-bound proteins from cultured human fibroblasts and hair root cells: qualitative and quantitative variation.

Proteins from cultured human fibroblasts and native human hair root cells were investigated using the two-dimensional electrophoresis (2DE) technique. Cell material from 35 different healthy persons was examined. Proteins of different sources were separated: total proteins of fibroblasts (12 cell lines), soluble proteins of fibroblasts (12 cell lines), structure-bound proteins of fibroblasts (eight cell lines) and soluble proteins of hair root cells (12 subjects). The protein samples of different individuals were run in pairs through the electrophoresis procedure and the two patterns of each pair were compared. All changes in the electrophoretic mobility of polypeptide spots (qualitative variants) and all clearly visible differences in the staining intensity of the spots (quantitative variants) were scored. Less than 1% of the qualitative variants per pattern was found in total cell proteins and this percentage was not increased in soluble proteins. No qualitative variation was detected in structure-bound proteins. Quantitative variation occurred to a considerably higher degree in the 2DE patterns than qualitative changes. The incidence of quantitative variants was about three times higher in soluble proteins (11%) than in structure-bound proteins (3.5%); in the total cell proteins it lay in between (7%). Cultured cells (fibroblasts) and native cells (hair root cells) showed a similar degree of variation. A comparison of the data shown here with data obtained by an investigation on inbred strains of the mouse suggest that the major part of the quantitative variants observed in the 2DE patterns of proteins were genetically determined. The results presented here and the mouse data mentioned above lead us to the conclusion that the genetic variability of proteins may be characterized by quantitative changes rather than by qualitative changes, and that the genetic variability occurs to quite different degrees in different classes of proteins: structure-bound proteins less than soluble non-enzymatic proteins less than enzymes (certain groups).