Example of Prokaryotic Transposable Element. (A) Genetic organization of the canonical Tn
Xax1 located in
X. citri subsp. citri strain 306 plasmid pXAC64. Genes are indicated by colored boxes, with the direction of transcription shown by the arrowheads. Transposition-related genes are shown in purple, and passenger genes in red and blue. The presumed resolution site is located between the
tnpT and
tnpS genes, as observed in the transposable element Tn
4651. This includes two palindromes: IR1 and IR2 are probably part of the core site at which recombination occurs, recognized by the TnpS recombinase, whereas IRa and IRb are potential binding sites for TnpT. The terminal inverted repeats (IRL and IRR) are shown as black triangles. The convention used for orientation of the transposon is that the transposase (TnpA) is transcribed from left to right. TnpA is closely related to other Tn
3-like elements from
Shewanella (IS
Sod9; 47% identity),
Acinetobacter (IS
Acsp1; 46%),
Arthrobacter (IS
Arsp6; 43%),
Azospirillum (IS
Azs17; 41%),
Salmonella (IS
Swi1; 42%), and
Nostoc (IS
Npu13; 43%) species and to the mercury resistance transposon Tn
5044 from
X. campestris (84%).
(B) IRs identified from other Tn
3-like transposable elements. All include the GAGGG tips sharing sequence similarities to Tn
Xax1 IRs. These are Tn
Pa43 from
Pseudomonas aeruginosa, Tn
Stma1 from
Stenotrophomonas maltophilia strain D457, Tn
Tin1 from
Thiomonas intermedia strain K12, and Tn
Xca1 from
X. campestris pv. vesicatoria plasmid pXCV183 (extracted from
Ferreira et al., 2015).