A Time-resolved Investigation of Ribosomal Subunit Association Original Research Article

The notion that the ribosome is dynamic has been supported by various biochemical techniques, as well as by differences observed in high-resolution structures of ribosomal complexes frozen in various functional states. Yet, the mechanisms and extent of rRNA dynamics are still largely unknown. We have used a novel, fast chemical-modification technique to provide time-resolved details of 16 S rRNA structural changes that occur as bridges are formed between the ribosomal subunits as they associate. Association of different 16 S rRNA regions was found to be a sequential, multi-step process involving conformational rearrangements within the 30 S subunit. Our results suggest that key regions of 16 S rRNA, necessary for decoding and tRNA A-site binding, are structurally altered in a time-dependent manner by association with the 50 S ribosomal subunits.