Tn5 transposase loops DNA in the absence of Tn5 transposon end sequences

Christian D. Adams, Bernhard Schnurr, Dunja Skoko, John F. Marko, William S. Reznikoff*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Transposases mediate transposition first by binding specific DNA end sequences that define a transposable element and then by organizing protein and DNA into a highly structured and stable nucleoprotein 'synaptic' complex. Synaptic complex assembly is a central checkpoint in many transposition mechanisms. The Tn5 synaptic complex contains two Tn5 transposase subunits and two Tn5 transposon end sequences, exhibits extensive protein-end sequence DNA contacts and is the node of a DNA loop. Using single-molecule and bulk biochemical approaches, we found that Tn5 transposase assembles a stable nucleoprotein complex in the absence of Tn5 transposon end sequences. Surprisingly, this end sequence-independent complex has structural similarities to the synaptic complex. This complex is the node of a DNA loop; transposase dimerization and DNA specificity mutants affect its assembly; and it likely has the same number of proteins and DNA molecules as the synaptic complex. Furthermore, our results indicate that Tn5 transposase preferentially binds and loops a subset of non-Tn5 end sequences. Assembly of end sequence-independent nucleoprotein complexes likely plays a role in the in vivo downregulation of transposition and the cis-transposition bias of many bacterial transposases.

Original languageEnglish (US)
Pages (from-to)1558-1568
Number of pages11
JournalMolecular Microbiology
Issue number6
StatePublished - Dec 2006

ASJC Scopus subject areas

  • Molecular Biology
  • Microbiology


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