Isolation and characterization of Tn7 transposase gain-of-function mutants: a model for transposase activation

Tn7 transposition has been hypothesized to require a heteromeric transposas e formed by two Tn7-encoded proteins, TnsA and TnsB, and accessory proteins that activate the transposase when they are associated with an appropriate target DNA, This study investigates the mechanism of Tn7 transposase activ ation by isolation and analysis of transposase gain-of-function mutants tha t are active in the absence of these accessory proteins, This work shows di rectly that TnsA and TnsB are essential and sufficient components of the Tn 7 transposase and also provides insight into the signals that activate the transposase, We also describe a protein-protein interaction between TnsA an d TnsC, a regulatory accessory protein, that is likely to be critical for t ransposase activation.