Part of the multicomponent carbazole 1,9a-dioxygenase (CARDO), that converts carbazole (CAR) into 2-aminobiphenyl-2,3-diol. Catalyzes the dioxygenation at the angular (C-9a) and adjacent (C-1) positions of carbazole to yield a highly unstable cis-hydrodiol intermediate which is spontaneously converted to 2-aminobiphenyl-2,3-diol. 9H-carbazole + H(+) + NADH + O2 = 2'-aminobiphenyl-2,3-diol + NAD(+) 9H-carbazole + H(+) + NADPH + O2 = 2'-aminobiphenyl-2,3-diol + NADP(+) Binds 1 [2Fe-2S] cluster per subunit. Homotrimer. Carbazole 1,9a-dioxygenase complex consists of a terminal oxygenase component CarAa, a ferredoxin reductase component fdr and a ferredoxin component CarAc (Probable).