A structural model of 5S RNA from E. coli based on intramolecular crosslinking evidence.

We describe new results obtained using the bifunctional chemical reagent phenyldiglyoxal (PDG) to study the intramolecular crosslinking of ribosomal 5S RNA from E. coli. In a previous publication (Wagner & Garrett [1]) we reported the identification of a crosslink in the stem region of 5S RNA (G2-G112) using the same reagent but were unable to obtain further information because of the presence of monofunctional adducts which confused the analyses. To overcome this problem, we have removed the monoaddition products by coupling them via their free reagent ends to a solid support bearing reactive groups. Using this system we have been able to identify a new crosslink G41-G72 in native 5S RNA which has considerable structural implications. We propose a structural model in which the proximity of both nucleotides is maintained by secondary interactions.