Composition and genetic variability of proteins from nuclear fractions of mouse (DBA/2J and C57BL/6J) liver and brain

Proteins from nuclear plasma of mouse liver and brain and from the nuclear membranes of mouse liver were separated by two-dimensional electrophoresis. For the purpose of comparison, liver cytosol proteins were also investigated. The protein samples were prepared from two inbred strains of the mouse (DBA/2J, C57BL/6J) and their hybrids. The patterns obtained were compared with regard to the composition and genetic variability (qualitative and quantitative variants) of proteins from different nuclear fractions and organs. The percentage (greater than 30%) of spots common to different organs (liver, brain), but from the same nuclear fraction (plasma) was greater than the percentage (less than 20%) of spots common to different cell and nuclear fractions (cytosol, nuclear plasma and nuclear membranes) of the same organ (liver). Quantitative genetic variants occurred much more frequently than qualitative genetic variants (5.1% vs. 0.2%; liver nuclear plasma). The incidence of genetic variants was much higher in liver (5.3%) than in brains (0.0%), and higher in solubilized nuclear proteins (5.3%) than in structure-bound nuclear proteins (2.1%).