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Group II intron secondary structure










         Group II introns have two main families of secondary structure, IIA and IIB. Each class is further divided into two subdivisions, A1, A2, B1 and B2, although A2 introns are very rare. Consensus structures for IIA and IIB are displayed by the links to the left (adapted from Michel et al., 1989 and Toor et al., 2001). More recently, class IIC has been recognized, and is represented by all introns in bacterial class C.

          We have made consensus RNA structures for all phylogenetic subclasses (the subclasses are based on ORF relationships). The mitochondrial class has a standard IIA1 structure; chloroplast-like class 1 has a standard IIB1 structure; chloroplast-like class 2 has a standard IIB2 structure; the remaining bacterial introns have somewhat “hybrid” and novel features. See Toor et al. 2001 for full description.









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