Identification of New Ribosomal Proteins and the Snalysis of the Change of Ribosomal Structure During the Transition of Cell Growth Phase in Escherichia Coli

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We developed a radical-free and highly reducing (RFHR) method of two dimensional polyacrylamide gel electrophoresis and identified five new protein components (A, B, C, D, and E) of E. coli ribosomes. The amino acid sequences of these new components were analyzed and all the gene loci were determined. That is to say, genes for A, B, C, D and E were localized at 37.6', 72', 88.5', 33' and 22', respectively. Proteins A, B, C and D were named L35, L36, pre L31 and S22, respectively, according to a unified nomenclature for E. coli ribosomal proteins. The discovery of the new ribosomal proteins in E. coli is unique since the establishment of the nomenclature in 1971. Protein E was classified as a ribosomal factor, because it released from ribosomal particles during high salt washing in the purification of ribosomes. The change of protein E dependent on the cell growth showed a strong pararellism with that of 70S dimer (100S), which was formed in the stationary phase of the cell growth. Protein E exists in 100S but not 70S monomer or free 50S, 30S subunits. The molar ratio of protein E to 100S is one to one. These results suggest that protein E may connect two 70S ribosomes and form 100S which has lost the activity of protein brosynthesis. The 100S, the forth mode of ribosomes, may be a form waiting for an improvement of the environment for the cell growth.