| Abstract: | Isolated trout testis nuclei rapidly incorporate alpha-32P]NAD+ into chromosomal proteins. Three proteins, very-lysine-rich histone (H1), a specific trout chromosomal protein (H6) and the sperm-specific protamines, incorporate the label as adenosine diphosphoribosyl (ADP-Rib) residues. No significant labeling of the nucleosomal 'core' histones H2A, H2B, H3 and H4 was observed. The linkage of the 32P](ADP-Rib) residues to each protein was very labile at pH values greater than 7.0 but by working at acidic pH and low temperatures the ADP-Rib label could be shown to be covalently bound to protein by gel electrophoresis and ion-exchange chromatography. The 32P]ADP-Rib chains could be removed by digestion with snake venom phosphodiesterase with the formation of AMP and phosphoribosyl-AMP. |
