190 



SUBCELLULAR PARTICLES 



NUCLEI 



I 

 extract with pH 7.1 phosphate buffer 



EXTRACT - 



( RNA + protein ) 

 /^Fraction IJ 



remove salt 

 extract with acid 



RESIDUE 



I 

 suspetid in 1 M NaCl 



centrifuge at 26 000 x g 



PRECIPITATE 

 extract with acetate buffer, pH 4 1 



EXTRACT - 



( histones ) 

 [Fraction III] 



- RESIDUE 



( Gelatinous protein ) 

 [Fraction IV] 



EXTRACT 



( arginine- and 

 lysine-rich histones ) 



RESIDUE 



f PNA + non-histone protein ) 

 [Fraction Vj 



Fig. 3. Flow-sheet for fractionation of proteins of isolated calf thymus nuclei. 



Table i. Al.anine-i-C incorporation into different protein fractions of thymus nuclei 



PROTEIN FRACTION 



Total nuclear protein 



Fraction I (protein-soluble in pH 7.1 buffer) 



Fraction II (residue after extraction in i m NaCl ) 



Fraction III (histones) 



Fraction IV (gelatinous protein) 



Fraction V (non-histone protein associated with DNA) 



Protein released to medium during incubation 



Fraction I 



Arginine-rich histones 



Lysinc-rich histones 



INCUBATION 

 TIME, MIN. 



90 



90 



90 



90 



90 



90 



30 

 60 

 90 

 30 

 60 

 90 



30 

 60 

 90 



30 

 60 

 90 



S. A., 



cpm/mg 



107 

 179 

 117 



36 



157 

 243 



5 



8 



16 



10 



66 

 105 

 2.3 

 4-5 

 6.7 



5.6 

 6.9 



