On the identity of nuclear membrane and non-histone nuclear proteins.

The fate of plasma and nuclear membrane polypeptides in preparations of acidic chromosomal protein from chicken erythrocytes has been investigated. It is shown that detergent extraction procedures (Nonidet P-40, Triton X-100, and saponin), commonly employed in the preparation of acidic chromosomal protein, cannot be relied upon to remove plasma and nuclear membrane polypeptides. These polypeptides persist in nuclear and chromatin preparations and subsequently fractionate as acidic chromosomal protein. In fact, the polypeptides in a preparation of erythrocyte acidic chromosomal protein are shown by gel electrophoresis in dodecyl sulfate to be almost identical to those in a preparation of erythrocyte nuclear membrane. The implication of these results for the preparation of acidic chromosomal protein is dicussed.