Fragments of Ribosomal Particles

Limited nuclease treatment of 30 S subunits yields two main fragments of unequal size one containing proteins S4, S5, S6, S8, S15, S17, S20, and possibly S13 or S14, and the other S7, S9, SIO, S19, and S13 or S14. Various smaller fragments have been isolated consisting of subsets of these two groups of proteins, the smallest one containing S8 and S15 and another one S7 and S19 (Morgan and Brimacombe, 1972, 1973 Roth and Nierhaus, 1973 Yuki and Brimacombe, 1975). 

A subdivision of 30 S proteins into three groups has been obtained by analyzing hydrolyzates of a protein-deficient reconstitution intermediate (RI) particle. In this case, the protein groups consisted of S4, SI6, SI7, and S20, with RNA from the 5 proximal region of the 16 S RNA S6, S8, S15, and S18, with RNA from the central region and S7, S9, S13, and S19, with RNA from the 3 proximal region (Zimmermann et al, 1974, 1975). 

The 50 S subunit is much more resistant to this mild nuclease treat- 

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