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Figure 2
The tertiary structure of Alcaligenes DAD. (a) The fold of the monomer viewed along the cupin barrel of the enzyme towards the iron-binding site which is formed by three invariant histidine residues (76, 78 and 114) and a putative carbonate ligand (shown in ball-and-stick representation with the iron coloured rust brown and its dative bonds as yellow dashes). Regions of β-strand are coloured pale green and the helical segments are shown in clay-red with the intervening loops in beige. Note that strand N0 partakes in one of the cupin-barrel sheets of the neighbouring monomer in the dimer. (b) A topology diagram of DAD showing the cupin-barrel sheets with residue numbers for all of the secondary-structure elements. The iron-binding site formed by His76, His78 and His114 in strands II and VII is shown, as is the involvement of strand N0 in the abutting β-sheet of the neighbouring monomer (pale grey stands at the back, labelled in italics).

Journal logoBIOLOGICAL
ISSN: 1399-0047
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