TNPI RECOMBINASE - IDENTIFICATION OF SITES WITHIN TN5401 REQUIRED FOR TNPI BINDING AND SITE-SPECIFIC RECOMBINATION

The Bacillus thuringiensis class II transposon Tn5401 encodes a recombinase protein, TnpI, that mediates the resolution of cointegrate molecules generated as intermediates during Tn5401 transposition by the TnpA transposase, This recombination event requires a specific target site, or internal resolution site, at which TnpI binds and catalyzes the exchange of DNA strands. Gel mobility shift assays and DNase I footprinting analyses were used to localize the TnpI binding region to the sequence extending from nucleotides 637 to 747 of Tn5401, Deletions within this region blocked TnpI-mediated recombination in vivo, The 12-bp sequence ATGTCC RCTAAY, present in four copies within the TnpI binding region, is proposed to be the recognition sequence for TnpI binding, TnpI also binds to a single copy of this sequence located within the 53-bp terminal inverted repeats of Tn5401, The unique juxtaposition of recombinase and transposase binding sites at the terminal inverted repeats of Tn5401 suggests that TnpI regulates the binding and/or catalytic activity of TnpA transposase.