Among kanamycin-resistant tranductants , the presence of the lexA ( Ind ) mutation was confirmed through β-galactosidase assay after introduction of the pGE108 plasmid ( Table 2 ) which contains a LexA-regulated cea ∷ lacZ fusion ( Salles et al. , 1987 ) .
The LexA-based genetic system detects in-vivo protein dimerization in E. coli SU101 , in which the reporter fusion sulA : : lacZ is controlled by the LexA dimer -LRB- dimerization is essential for operator recognition -RRB- .