Difference between revisions of "General Information/ IS derivatives of Tn3 family transposons"
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|[[Image:1.15.2.png|thumb|center|510x510px|'''Fig. 1.15.2.''' Tn''3'' family resolvase configuration. | |[[Image:1.15.2.png|thumb|center|510x510px|'''Fig. 1.15.2.''' Tn''3'' family resolvase configuration. | ||
− | A) Tn''3'' has divergent transposase and resolvase (serine recombinase) genes with a res ( | + | A) Tn''3'' has divergent transposase and resolvase (serine recombinase) genes with a res (resolution, recombination site between the divergent genes. It includes 3 sites at which resolvase binds (I, II and III). |
B) Tn''501'' carries co-linear transposase and resolvase genes with the res site upstream of the resolvase. | B) Tn''501'' carries co-linear transposase and resolvase genes with the res site upstream of the resolvase. | ||
− | C) Tn''4430'' has a similar configuration as | + | C) Tn''4430'' has a similar configuration as Tn501 but its resolvase is a tyrosine recombinase and its res site, upstream of the resolvase has a more complex structure |
D) TnXax1 carries two divergent genes, tnpS (a serine recombinase) and tnpT (a helper gene). The resolution site lies between the two genes and has a complex structure. |alt=]] | D) TnXax1 carries two divergent genes, tnpS (a serine recombinase) and tnpT (a helper gene). The resolution site lies between the two genes and has a complex structure. |alt=]] |
Revision as of 12:13, 2 June 2020
Another source of ambiguity for classification purposes occurs in the Tn3 family (see section “Tn families”) (Fig.1.15.1 and 1.15.2). Tn3 family members are quite variable. They include a number of diverse passenger genes that can represent entire operons, notably mercury resistance, or individual genes involved in antibiotic resistance, breakdown of halogenated aromatics, or virulence [e.g. [1]]]. They often carry integron recombination platforms enabling them to incorporate additional resistance genes by recruiting integron cassettes. Members are quite characteristic: they have long relatively well conserved IR and a particularly long Tpase (950 to 1025 aa). They also encode a site-specific recombination (“resolution”) system necessary for completion of their transposition (Grindley 2002). There are a number of different resolution systems associated with different members of this family (Fig.1.15.2) IS1071, (Fig.1.15.1) composed of Tn3-like IR and Tpase gene but lacking both the site-specific recombination system and passenger genes was identified many years ago[2][3]. This clearly accords with the definition of an IS. Several other examples have now been identified (e.g. ISVsa19, ISShfr9, ISBusp1).