Specific Ribonucleoprotein Fragment from the 30S Subunit of <Emphasis Type="Italic">E. coli</Emphasis> Ribosomes

WE describe here a new approach to the determination of the three dimensional arrangement of the proteins within the ribosome, based on controlled degradation with nuclease. We suggest that by isolating ribonucleoprotein (RNP) fragments and determining which particular proteins each fragment contains, it should eventually be possible to construct a detailed “map” of the protein arrangement. The “mapping” problem has already received attention in various laboratories. Mizushima and Norrtura¹ have shown that the proteins of the E. coli 30S ribosomal subunit assemble with 16S RNA in a highly specific order. Further, the reactivity of the 30S particle towards proteolytic enzymes² and protein-modifying reagents³ shows a striking correlation with Mizushima and Nomura's “assembly map”¹, in that the first group of proteins in the assembly process seems to be protected in the completed particle.