ON THE CONFORMATION OF THE ALPHA SARCIN STEM-LOOP OF 28S RIBOSOMAL-RNA

A synthetic RNA that is a substrate for the cytotoxin alpha-sarcin has been examined by NMR. The molecule in question includes the entire sequence of the so-called alpha-sarcin loop from rat 28S rRNA (U4316-C4332), and it is cleaved at the residue that corresponds to G4325, the site of alpha-sarcin cleavage in 28S rRNA. The data show that the terminal stem designed into the molecule's sequence exists, as expected, and that its loop has a definite structure, which is stable to at least 40-degrees-C under ionic conditions compatible with its cleavage by alpha-sarcin.