FIG. 1.

Multiple amino acid sequence alignment of Qdo, Hod, and some hydrolases and cofactor-free haloperoxidases performed with the program CLUSTAL W (55), and prediction of secondary-structure elements for Qdo and DhlA. Abbreviations: Qdo, P. putida 33/1 1H-3-hydroxy-4-oxoquinoline 2,4-dioxygenase (35; EMBL accession no. Y14779); Hod, A. ilicis Rü61a 1H-3-hydroxy-4-oxoquinaldine 2,4-dioxygenase (35; EMBL accession no. Y14778); Tpes, P. putida atropinesterase (20); CpoL, Streptomyces lividans TK64 chloroperoxidase (4); BpoA2, Streptomyces aureofaciens ATCC 10762 bromoperoxidase (45); XylF, P. putida 2-hydroxymuconic semialdehyde hydrolase (23; the sequence has been corrected in the N-terminal region according to reference 12; see also reference 22); DhlA, Xanthobacter autotrophicus GJ10 haloalkane dehalogenase (26). The numbering does not refer to any of the sequences. Presumed triad residues are marked with a star and printed in boldface. Conserved amino acid motifs surrounding the catalytic nucleophile and the catalytic histidine residue of the α/β hydrolase-fold enzymes are enclosed in a box. S93, D120, and S213 of Qdo are marked by an arrow. The first line at the bottom of the sequences shows the secondary-structure elements of Qdo as calculated by the program PredictProtein (50). The second and third lines indicate the secondary-structure elements of DhlA as predicted (line 2) and as deduced from the X-ray analyses of DhlA (56) (line 3). Hatched and open boxes indicate β-sheets and α-helices, respectively. The α-helices of DhlA are numbered according to the numbering scheme of Verschueren et al. (56). Note that the Qdo sequence (35) has been corrected in the C-terminal region (FLQA instead of FLHGLSTCNHELKR) and at position 98 (C instead of V). Qdo thus consists of 264 amino acids, its calculated molecular mass is 30,347 Da, and its calculated isoelectric point is pH 5.43.