Among polychlorinated dibenzo-p-dioxins (PCDDs), 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TetraCDD) is the most toxic one. Recently, we reported that rat CYP1A1 mutant, F240A, expressed in yeast showed metabolic activity toward 2,3,7,8-TetraCDD. In this study, we successfully expressed N-terminal truncated P450s (Delta 1A1 and Delta F240A) in Escherichia coli cells. Kinetic analysis using membrane fractions prepared from the recombinant E. coli cells revealed that Delta F240A has enzymatic properties similar to F240A expressed in yeast. The metabolism of PCDDs by recombinant E. coli cells expressing both Delta F240A and human NADPH-P450 reductase was also examined. When 2,3,7-TriCDD was added to the E. coli cell culture at a final concentration of 10 mu M, approximately 90% of the 2,3,7-TriCDD was converted into multiple metabolites within 8 h. These results indicate the possible application of prokaryotic cells expressing Delta F240A to the bioremediation of PCDD-contaminated soil.