Tightly bound nonprotamine proteins from ram sperm nuclei studied by one- and two-dimensional peptide mapping

The tightly bound proteins of ram sperm nuclei (TBSP) have been recovered as a fraction co-sedimenting with DNA after high salt-urea deprotamination of the nuclei. TBSP were studied by two-dimensional (2D)tryptic peptide mapping and by one-dimensional (1D)-partial proteolysis mapping. The 2D maps revealed a strong homology among the proteins, irrespective of substantial differences in their molecular masses. This homology was supported also by the 1D-mapping data.The 2D-tryptic maps of TBSP were compared to those of lamb liver lamins but no apparent similarity was detected. TBSP were found to react positively to a test for the presence of carbohydrate residues, suggesting that these proteins are glycoproteins as established earlier for the lamins.The 2D maps of several proteins of seminal plasma origin, used as a control, displayed completely different peptide profiles.