An integron is a two component gene capture and dissemination system, initially discovered in relation to antibiotic resistance, and which is found in plasmids, chromosomes and transposons. The first component consists of a gene encoding a site-specific recombinase along with a specific site for recombination, while the second component comprises fragments of DNA called gene cassettes which can be incorporated or shuffled.
A cassette may encode genes for antibiotic resistance, although most genes in integrons are uncharacterized. An integron contains an integrase (int1) related to those of a phage, followed by an attI site for integration of cassettes and recognition of the integrase, and a promoter to drive expression. An integron may appear in a plasmid or on the chromosome. An attC sequence (also called 59-be) is a repeat that flanks cassettes and enables cassettes to be integrated at the attI site, excised and undergo horizontal gene transfer.
A functional integron "platform" requires:
- an integrase: intI, a tyrosine recombinase responsible for incorporation into the genome
- a proximal recombination site: attI, which acts as the locus for reincorporation to the genome. It combines with a attC site at the insertion site.
The term super-integron was first applied in 1998 (but without definition) to the integron with a long cassette array on the small chromosome of Vibrio cholerae. The term has since been used for integrons of various cassette array lengths or for integrons on bacterial chromosomes (versus, for example, plasmids). Use of "super-integron" is now discouraged since its meaning is unclear.
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- Journal of Bacteriology, June 2002, p. 3017-3026, Vol. 184, No. 11 article Characterization of the Class 3 Integron and the Site-Specific Recombination System It Determines
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- INTEGRALL The Integron Database
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