Quantitative solubilization of nonhistone chromosomal proteins without denaturation using zwitterionic detergents.

Of three kinds of commercial zwitterionic detergents [SB 12, SB 14, and 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (Chaps)], SB 12 and Chaps were more useful than SB 14 because of high solubility and less interference with protein assay. Efficiency for protein solubilization at pH 6-9 was higher for SB 12 than for Chaps with either calf thymus chromatin or rat liver nuclei. At pH 9 and ionic strength (I) = 0.35, 1% SB 12 and 1% Chaps were capable of solubilizing about 70% and about 47% of total proteins in rat liver nuclei, respectively. Core histones in rat liver nuclei were extracted to a lesser extent with Chaps than with SB 12. DNA-dependent RNA polymerase and isopeptidase activities were barely inactivated by 1% Chaps at pH 8-9, but isopeptidase activity was inhibited by 0.3% SB 12. These facts indicate that whereas SB 12 is effective for solubilization of whole nuclear proteins, Chaps is suitable for the selective extraction of nonhistone chromosomal proteins without denaturation.