Fig 8. Int^pTN3-promoted low sequence specificity reactions on exogenous sequences.

A. Low sequence specificity reactions mimicking homologous DNA integration are visualized by the accumulation of multimers of increasing size only when the reaction occurs in the presence of wild-type Int^pTN3. A linear pBR322 species generated by Int^pTN3-generated double-strand cleavage is visible and migrates close to a control plasmid digested by the EcoRI endocnuclease. OC and SC refer to the open circle and supercoiled DNA forms, respectively. B. Int^pTN3 catalyzes inversion on linear DNA substrates between two inverted E. coli lacZ gene segments of varying sizes separated by a Kanamycin resistance determinant. The sequence identity between the inverted segment amounts to 250, 175 and 100bp respectively in plasmids pCB574, pCB572 and pCB538 (see Materials and methods). White arrowheads refer to original fragments and black arrowheads indicate inversions products. Int^pTN3 concentration multipliers refer to the standard assay described in Materials and Methods.