Diagrams:

Mechanism of tmRNA Action

Standard tmRNAs
· Escherichia coli
· Synechococcus elongatus
· Clostridium botulinum (after intron removed)

Two-Piece tmRNAs (from permuted genes)
· Prochlorococcus marinus
· Caulobacter crescentus
· Agrobacterium tumefaciens
· Rickettsia prowazekii
· Reclinomonas mitochondrion (no tag reading frame)

Group I Intron of C. botulinum

SmpB structure
SspB in complex with AANDENYALAA tag peptide