Organization of ribosomal protein genes of Escherichia coli as analyzed by polar insertion mutations.

Several mutants of lambdaspc1 and lambdafus3 have been isolated carrying DNA insertion elements that were selected for their ability to reduce the expression of the spc gene. The sizes and locations of the insertions on the phage genomes were determined by heteroduplex analysis. They were found to be located at different positions in the Spc transcription unit. The effect of these insertions on the expression of the ribosomal protein genes carried by these phages in ultraviolet light-irradiated bacteria was investigated. The insertions at intermediate positions in the transcription unit reduced the expression of some of the genes in the unit but not others. Assuming that the genes whose expressions were reduced are distal to the insertion, it was possible to determine the relative position of most of the genes in the unit. The results indicate the order of genes in the Spc transcription unit is: promoter, L14, L24, L5, S14, S8, L6, L18, (S5, L15, L30).