Sequential Folding of Transfer RNA. A Nuclear Magnetic Resonance Study of Successively Longer tRNA Fragments with a Common 5’ End

John Boyle, George T. Robillard, Sung-Hou Kim

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    Abstract

    Most folding studies on proteins and nucleic acids have been addressed to the transition between the folded and unfolded states of an intact molecule, where an entire residue sequence is present during the folding event. However, since these polymers are synthesized sequentially from one terminus to the other in vivo, their folding pathways may be influenced greatly by the sequential appearance of the residues as a function of time. The three-dimensional structure of yeast tRNAPhe in the crystalline state is correlated with 360 MHz proton nuclear magnetic resonances from three fragments plus an intact molecule of the tRNA that share a common 5’ end and are in a solution condition similar to that of the crystal structure. This has allowed identification of folded structures present in the fragments and presumably present in the growing tRNA molecule as it is being synthesized from the 5’ end. The experiments show that only the correct stems are formed in the fragments; no additional or competing helical region is produced. This suggests that in the biosynthesis of this tRNA, correct folding of helical stems occurs before the entire molecule is formed. Further, some of the tertiary interactions (hydrogen bonds) found in the crystal structure are also probably present before the synthesis is completed. These findings are generalized to consider the precursor of the tRNA as well as other tRNAs.
    Original languageEnglish
    Pages (from-to)601-625
    Number of pages25
    JournalJournal of Molecular Biology
    Volume139
    Publication statusPublished - 1980

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