| Description | An integron is a system that enables capture and expression of small mobile elements called cassettes. Examples that include large numbers of cassettes, as in Vibrio cholerae El Tor N16961, have been called super-integron, but it is suggested that this term should be deprecated, and no distinct property will be built. An integron should contain an intI gene, of any of several classes, encoding an integrase. It should have a promoter to drive expression, an attI site, ability to incorporate cassettes, and multiple attC sites (also called 59-base element) flanking the cassettes. The attC sites may exhibit high homology to each other in a long integron, but are best recognized by imperfect dyad symmetry at their outer ends. A single genome may have several integrons, and one integron may contain dozens of cassettes. Note that an integron cassette with a defective integron integrase, carried by a Tn7 transposon, is called a class 2 integron. |
