VII. SYNTHESIS OF RNA AND RIBOSOMES 



303 



Methionine (about 47%), alanine (about 377^ ), and serine (about 11%) 

 account for most of the NHo terminal amino acids and the average 

 molecular weight of the individual protein components estimated from 

 the proportion of NHo terminal amino acids is 25,000 (Waller and 

 Harris, 1961). Since the molecular weight of the total protein of the 

 308 particle is only 260,000, any one 30S particle could include only 

 about 10 of the observed components. 



2. Ribosomal Enzymes 



Latent ribonuclease (RNase) was found in chemically isolated ribo- 

 nucleoprotein of E. coli. The enzyme was not active until the structure 

 of the nucleoprotein was disrupted (Elson, 1958, 1959). 



.300 - 



E 

 O 

 CO 

 00 



Q 

 O 



.200 - 



.100 - 



- 80 



- 60 



40 £ 



UJ 



- 20 



Bottom 



10 



20 25 Top 



Fraction number 



Fig. 7. Sedimentation analysis shows a correspondence between ribosomes indi- 

 cated by optical density (O.D.) and /?-galactosidase activity. (Cowie et al., 1961.) 



Latent RNase also appeared in ribosomes isolated by centrifugation 

 or chromatography. Furthermore, the total cellular content of RNase 

 could be attributed to the RNase of the ribosomes (Bolton, 1958). The 

 enzyme is either localized in 30S particles exclusively (Elson and Tal, 



