A Series of Specific Ribonucleoprotein Fragments from the 30‐S Subparticle of Escherichia coli Ribosomes

1 30-S ribosomal subparticles were hydrolysed with ribonuclease T1 or pancreatic ribonuclease in the presence of 2 M urea. The RNA · protein fragments produced were separated on 5% polyacrylamide/0.5% agarose composite gels. Fractions from the composite gels were subjected to protein analysis on 17.5%, periodate-soluble polyacrylamide gels run in the detergent sarkosyl, using the technique already published. 2 Several RNA · protein fragments were obtained by this procedure, each containing equimolar amounts of a few specific ribosomal proteins. Strict criteria for specificity of the proteins in each fragment were applied. Proteins S8 and S15 were found reproducibly in a small RNA · protein fragment, with only trace amounts of the remaining ribosomal proteins. Six proteins (S7, S9, S10, S13, S14, and S19) constitute another group, and fragments containing three, four, five, or all six of these proteins were observed. Protein S20 was occasionally associated with this group, or with S6, S16 or S17, and possibly S21. The latter (including S20) were also found in association with S8 and S15. 3.The individual proteins found in specific fragments are interpreted as being close neighbours in the 30-S particle. The fragment data can be incorporated into a re-arranged version of Nomura's “assembly map”.