RNA can bind and sense the shapes of other molecules by feeling them with its backbone—and not just its bases. What gives RNA molecules this remarkable versatility?
By Anna Marie Pyle
What pulls catalytic RNA together
Group II introns have a conserved secondary structure consisting of six domains (magenta) that are flanked by the upstream and downstream exons (orange). In the first step of splicing (1), a bulged adenosine in domain 6 (DVI) attacks the phosphate at the 5′-splice site, becoming covalently attached to it and releasing the 5′-exon. In the second step of splicing (2), the 5′ terminus attacks the phosphate at the 3′-splice site, thereby joining the two exons (splicing them together) and releasing the lariat-shaped group II intron. The group II intron’s crystal structure is shown above, with the catalytically important domain V (DV) marked in magenta.