Many RNAs need Mg2+to produce stable tertiary structures. Here we describe a simple method to measure the rate and activation parameters of tertiary structure unfolding that exploits this Mg2+dependence. Our approach is based on mixing an RNA solution with excess EDTA in a stopped-flow instrument equipped with an absorbance detector, under conditions of temperature and ionic strength where, aft...

Wybutine (Ywye), situated next to the 3'-side of the anticodon of tRNAPhe from Saccharomyces cerevisiae, can be photo-crosslinked to mRNA when bound to Escherichia coli ribosomes. Crosslinking can be obtained with poly(U) as well as with oligonucleotides such as pAUGUUU or p(U)6. In order to identify the site of reaction on the mRNA, 5'-[32P]-labelled pAUGUUU was crosslinked by irradiation at 3...

Chemical reactivity of cytosines in 32P-labeled E. coli tRNA1Leu, E. coli tRNAPhe and yeast tRNAPhe before and after aminoacylation was examined by use of a cytosine-specific reagent, semicarbazide-bisulfite mixture. In all the three tRNA species examined, the cytosine residues that were susceptible to the modification were the same in the aminoacylated tRNA and the unacylated tRNA. Only a limi...

Rat liver 5 S and 5.8 S rRNAs were oxidized with periodate and the 3' termini were coupled to Sepharose 4B through an adipic acid dihydrazide spacer. Ribosomal proteins were passed through the nucleic acid affinity columns to form ribonucleoprotein complexes containing the nucleic acid and the proteins that bind to it (5 S . L6, L7, L19; and 5.8 S . L6, L19, S9, S13). Pure isoaccepting species ...

High resolution cryoEM of mammalian mitoribosomes revealed the unexpected presence of mitochondrially encoded tRNA as a structural component of mitochondrial large ribosomal subunit (mt-LSU). Our previously published data identified that only mitochondrial (mt-) tRNAPhe and mt-tRNAVal can be incorporated into mammalian mt-LSU and within an organism there is no evidence of tissue specific variat...