EFFECTS OF SPERMINE ON THE RIBONUCLEOPROTEIN PARTICLES 247 



in which relatively low binding of spermine occurred but the addition of 

 Mg + + increased it (Exps. i, 2, 3) ; one in which an intermediate uptake of 

 spermine occurred and Mg + + had little effect (Exps. 4, 5); and one in 

 which high binding of radioactive spermine occurred but the addition of 

 Mg + + decreased this binding (Exps. 6, 7). The possible reasons for these 

 variations will be discussed below. 



That the binding of the spermine is primarily due to the RNA of the 

 particles can be inferred from the concluding data. First, washing of the 

 particles with TCA releases most of the spermine counts (cf. footnote, 

 Table IV), indicating a non-covalent bond. Secondly, it can be seen 

 (Table V and F'ig. i) that the radioactive spermine which is bound to the 

 particles can be largely removed by treating the particles with either GTP 

 or ATP, and in doing so the RNA is also removed. Figure i shows that 

 as the bound spermine is removed from the particles, the RNA is propor- 

 tionally removed, whereas very little protein is lost. Hence, the ratio, 

 RNA /protein, follows the removal of the spermine and of the RNA, as 

 the GTP concentration is increased. Table V also indicates that when 

 Mg + + is incubated along with the GTP or ATP, the removal of spermine 

 by GTP or ATP is largely prevented, indicating that the added Mg + + 

 effectively forms a complex with the added GTP or ATP and prevents 

 its action in removing the spermine and the RNA. Thus it can be deduced 

 that the amine groups of the bound spermine were salt-bonded to the 

 phosphate groups of the RNA, and the addition of the pyrophosphate 

 compounds, GTP or ATP, effectively competes with the phosphate 

 groups of the RNA, for the bound spermine. When Mg + + was present, 

 the pyrophosphate groups were complexed with it, and hence had little 

 effect. 



Discussion 



Firstly, it should be understood that the pancreatic RNP particles do 

 not seem to be quite the same as the bacterial and yeast or even the liver 

 particles. Their size is different ; 150 A for the 85 S pancreatic particles [7], 

 and 200 A for the 80 S yeast particles [8] and for the 70 S Escherichia coli 

 particles [9, 10]. Furthermore, it appears that the E. coli particles are made 

 up of sub-units of 30 S and 50 .S" particles [9, 10, 11, 12] and of 100 S 

 dimers [9, 10, 11]. There is no evidence as yet, either morphologically or 

 with the analytical centrifuge, that the pancreatic particles are made up of 

 smaller units. There is evidence, though, that this might be the case for 

 the 80 S pea seedling particles [13] and the 80 S liver particles [14], but 

 even in these cases the sub-units seem to be 60 S and 40 S particles [13, 

 14]. In all the cases mentioned, except for pancreas, a decrease in the Mg + + 

 content of the particles results in their disruption, so that the smaller 



