R-proteins in modification deficient ribosomes - free 50S subunits

Ribosomal RNA modifications are introduced by specific enzymes during ribosome assembly in bacteria. Deletion of individual modification enzymes has a minor effect on bacterial growth, ribosome biogenesis, and translation, which has complicated the definition of the function of the enzymes and their products. We have constructed an E. coli strain lacking 10 genes encoding enzymes that modify 23S rRNA around the peptidyl-transferase center. This strain exhibits severely compromised growth and ribosome assembly, especially at lower temperatures. Ribosomal protein composition of the mature 50S ribosomes and free 50S subunits was analyzed by SILAC based qMS approach. We have found that absence of 23S rRNA modifications around PTC does not affect significantly r-protein content of incompletely assembled 50S or mature 50S ribosomes.