Circularly permuted "ssrA" has been reported in three major lineages: i) all alphaproteobacteria and the primitive mitochondria of jakobid protists, ii) two disjoint groups of cyanobacteria ("Gloeobacter" and a clade containing "Prochlorococcus" and many "Synechococcus"), and iii) some members of the betaproteobacteria ("Cupriavidus" and some Rhodocyclales). All produce the same overall two-piece (acceptor and coding pieces) form, equivalent to the standard form nicked downstream of the reading frame. None retain more than two pseudoknots compared to the four (or more) of standard tmRNA.