A preliminary three-dimensional arrangement of the proteins in the Escherichia coli 30-S ribosomal sub-particle.

Abstract

30‐S ribosomal subparticles from Escherichia coli were hydrolysed with ribonuclease T1, pancreatic ribonuclease or micrococcal nuclease in the presence of 2 M urea, and various concentrations of magnesium and ethanol. The RNA · protein fragments produced were separated on 5% polyacrylamide/agarose composite gels, and fractions from these gels were subjected to protein analysis on 17.5% periodate‐soluble polyacrylamide gels run in the detergent sarkosyl, using the technique already published. A wide range of RNA · protein fragments was obtained by this procedure, each containing a few specific ribosomal proteins. The strict criteria already published for determining the specificity of the proteins in each fragment were applied. The RNA · protein fragments divide into two distinct groups, those containing some or all of proteins S7, S9, S10, S13, S14 and S19, and those containing some or all of proteins S4, S5, S6, S8, S11, S15, S16(17), S18 and S20. Proteins S1, S2, S3, S12 and S21 were not found in specific fragments. The individual proteins found together in specific RNA · protein fragments are interpreted as being close neighbours in the 30‐S particle. The range of fragments observed is sufficient to enable the data to be combined with Nomura's “assembly map” and data from protein crosslinking experiments, into a preliminary three‐dimensional arrangement of the proteins.