| STRUCTURE |
Cross-linking yields better picture of intron Chemists at the University of Texas, Austin, have put together the best structural picture yet of a catalytic RNA molecule called the group II intron. This ribozyme is a model system for human introns, stretches of noncoding RNA that are present in nascent RNA transcripts. To produce protein-encoding messenger RNAs, these introns excise themselves and stitch together the remaining stretches of RNA. Now, professor Alan M. Lambowitz and postdoc James W. Noah have used UV cross-linking to glean unprecedented insight into the group II intron’s 3-D structure [Biochemistry, 42, 12466 (2003)]. During UV cross-linking, parts of the intron that are close to one another in space are covalently linked. One of the cross-links suggests a novel arrangement of domains at the intron’s active site. Lambowitz and Noah also observe that high Mg2+ concentrations force the intron into a rigid structure, whereas binding of the protein that helps the intron fold stabilizes only critical regions, allowing others to remain flexible. This observation suggests that parts of the intron’s active structure are different from what previous studies had indicated |
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