FIG. 5.

Sequence alignment of the subunits of protocatechuate 3,4-dioxygenases. Positions identical in both α and β subunits of all four enzymes are highlighted by black boxes; those identical in only one subunit of all four enzymes are shaded. Numbers above the sequences refer to positions in the alignment, not in a single sequence. Amino acid residues which for the enzyme of P. putida ATCC 23975 have been found to be involved in the active site are indicated by downward-pointing arrows; iron ligands by upward-pointing arrows (above the alignment for the α subunit and below the alignment for the β subunit) (45). Accession numbers and references for the published sequences: M30791 (74), M33798 (24), and L14836 (19).