Tn3 transposon

The Tn3 transposon is a 4957 base pair mobile genetic element, found in prokaryotes. It encodes three proteins:

β-lactamase, an enzyme that confers resistance to β-lactam antibiotics (and is encoded by the gene Bla).

Tn3 transposase (encoded by gene tnpA)

Tn3 resolvase (encoded by gene tnpR)

Initially discovered as a repressor of transposase, resolvase also plays a role in facilitating Tn3 replication (Sherratt 1989).

The transposon is flanked by a pair of 38bp inverted repeats.

Mechanism of replication

Step 1 - Replicative Integration

This first stage is catalysed by transposase.

The plasmid containing the transposon (the donor plasmid) fuses with a host plasmid (the target plasmid). In the process, the transposon and a short section of host DNA are replicated. The end product is a 'cointegrate' plasmid containing two copies of the transposon.

Shapiro (1978) proposed the following mechanism for this process:

Four single-strand cleavages occur - one on each strand of the donor plasmid and one on each strand of the target plasmid.

This page contains text from Wikipedia, the Free Encyclopedia - https://wn.com/Tn3_transposon

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Tn3 transposon

Mechanism of replication

Step 1 - Replicative Integration

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