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Biosynthesis of ribosomes in Pseudomonas aeruginosa. Medveczky, Nicholas E.


The structure ribosomes of Pseudomonas aeruginosa and Escherichia coli were compared. The thermal denaturation profiles of the P. aeruginosa ribosomes were consistently at higher temperatures than the corresponding profiles for those of E. coli. The differences in the thermal denaturation profiles of the ribosomal RNAs were not as pronounced. Although the numbers of the proteins resolved from the ribosomal subunits of E. coli and P. aeruginosa were approximately the same, the distribution of these proteins in the gel was markedly different. The optimum conditions for the resynthesis of ribosomes in P. aeruginosa have been established. It was demonstrated that the resynthesis of ribosomes proceeds through a number of ribosomal precursors. By isotope labelling experiments the rate of labelling of the RNA moiety of the ribosome was found to be different from the rate of labelling of the protein moiety. Furthermore both labels were found to accumulate in the ribosomes at the expense of the ribosomal precursors. The following precursors were resolved by sucrose density gradient centrifugation: 16S → 20S →23S → 25S →28S→30S → 32S → 34S → 40S → 43S → 50S The 16S to 28S precursors were not characterized well enough to be placed either in the 50S or 30S sequence. There was evidence that the ribosomal RNA itself had precursors, 9S and 12S.

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