HIGHER-PLANT 5S RIBOSOMAL-RNAS SHARE COMMON SECONDARY AND TERTIARY STRUCTURE - A NEW 3 DOMAINS MODEL

A new model of secondary and tertiary structure of higher plant 5S RNA is proposed. It consists of three helical domains: domain α includes stem I; domain β contains stems II and III and loops B and C; domain γ consists of stems IV and V and loops D and E. Except for, presumably, a canonical RNA-A like domain α, the two remaining domains apparently adopt a perturbed RNA-A structure due to irregularities within internal loops B and E and three bulges occurring in the model. Bending of RNA could bring loops B and E and/or C and D closer making tertiary interactions likely. The model differs from that suggested for eukaryotic 5S rRNA, by organization of domain γ. Our model is based on the results of partial digestion obtained with single-and double-strand RNA specific nucleases. The proposed secondary structure is strongly supported by the observation that crude plant 5SrRNA contains abundant RNA, identified as domain γ of 5SrRNA. Presumably it is excised from the 5S rRNA molecule by a specific nuclease present in lupin seeds. Experimental results were confirmed by computer-aided secondary structure prediction analysis of all higher plant 5S rRNAs. Differences observed between earlier proposed models and our proposition are discussed. © 1990.