Studies on the Secondary Structure of Wheat 5.8 S rRNA

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Abstract
The nucleotide sequence of wheat (Triticum aestivum) 5.8-S ribosomal RNA was re-examined using partial chemical degradation with high-temperature sequencing gels and oligonucleotide analysis. The results clarify previously ambiguous residues and add 2 additional nucleotides, G127 and G135, to the sequence. Estimates of the secondary structure suggest that 5.8-S rRNAs of higher lants differ from previous examples in having more open G + C-rich and A + U-rich stems. S1 RNase digestion was used to probe this secondary structure; the data generally support the ''burp gun'' model proposed for all 5.8-S rRNAs but are also consistent with a more open A + U-rich stem. Diethyl pyrocarbonate reactivity was used to probe the topography of this RNA in wheat ribosomes. The G + C-rich and A + U-rich stems are accessible to chemical modification in the wheat ribosome and suggest that the A + U-rich stem undergoes a significant conformational change when the molecule associates into ribosomes.