Acidic proteins of mammalian nuclei: isolation and characterization.

Abstract

Nonhistone protein was extracted from mammalian nuclei by 4 M buffers at pH 11. 6. Amino acid analysis of this acid-insoluble protein fraction demonstrated it to be acidic. Acrylamide gel electrophoresis of the protein fraction obtained from liver nuclei and from chromatin showed the nonhistone proteins to be composed of a similar and heterogeneous group of molecules. The electrophoretic pattern of the nonhistone proteins isolated from the livers of the mouse and the rat were similar. Radioactive orthophos-phate was rapidly incorporated into the phosphoserine and phosphothreo-nine of the proteins. P32 was associated with some of the protein bands on gel electrophoresis.