Document Detail

Visualization of a tertiary structural domain of the Tetrahymena group I intron by electron microscopy.
MedLine Citation:
PMID:  7508985     Owner:  NLM     Status:  MEDLINE    
The P4-P6 domain RNA of the group I intron of Tetrahymena thermophila has previously been shown by chemical probing to be an independently folding domain of the intron's tertiary structure. To directly visualize this tertiary structure, the P4-P6 domain and two folding defective mutants were prepared for high-resolution electron microscopy using tungsten shadowcasting. In the presence of Mg2+, the P4-P6 domain predominantly consists of compact molecules, while the two mutant RNAs are nearly all rod-like molecules. The measured length of the rod-like molecules is 64 (+/- 6) bp, which agrees closely with the length expected for molecules containing secondary structure only. In the absence of Mg2+, the P4-P6 domain contains threefold or tenfold fewer compact structures (depending on the mounting procedures) than in the presence of Mg2+. These results provide direct evidence for the overall shape of the tertiary structure proposed on the basis of biochemical experiment, and they confirm the Mg2+ dependence of tertiary folding. An equilibrium between the extended (rod-like) and the compact structures is suggested, with the concentration of bound Mg2+ and different mounting methods influencing the direction of the equilibrium. The entire group I ribozyme (L-21 Sca I RNA) was also examined by electron microscopy in the presence of Mg2+, and was revealed to have a compact shape. These studies present a direct demonstration of long-range interactions in a catalytic RNA molecule.
Y H Wang; F L Murphy; T R Cech; J D Griffith
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of molecular biology     Volume:  236     ISSN:  0022-2836     ISO Abbreviation:  J. Mol. Biol.     Publication Date:  1994 Feb 
Date Detail:
Created Date:  1994-03-21     Completed Date:  1994-03-21     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  2985088R     Medline TA:  J Mol Biol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  64-71     Citation Subset:  IM    
Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill 27599-7295.
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MeSH Terms
Base Sequence
Microscopy, Electron
Molecular Sequence Data
Nucleic Acid Conformation*
RNA / genetics,  ultrastructure*
RNA, Catalytic / genetics,  ultrastructure*
Tetrahymena thermophila / genetics*
Grant Support
Reg. No./Substance:
0/RNA, Catalytic; 63231-63-0/RNA; 7439-95-4/Magnesium

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