Crystal structure of dodecameric vanadium-dependent bromoperoxidase from the red algae Corallina officinalis

The three-dimensional structure of the vanadium bromoperoxidase protein fro m the marine red macroalgae Couallina officinalis has been determined by si ngle isomorphous replacement at 2.3 Angstrom resolution. The enzyme subunit is made up of 595 amino acid residues folded into a single alpha + beta do main. There are 12 bromoperoxidase subunits, arranged with 23-point group s ymmetry. A cavity is formed by the N terminus of each subunit in the centre of the dodecamer. The subunit fold and dimer organisation of the Cor. offi cinalis vanadium bromoperoxidase are similar to those of the dimeric enzyme from the brown algae Ascophyllum nodosum, with which it shares 33 % sequen ce identity. The different oligomeric state of the two algal enzymes seems to reflect separate mechanisms of adaptation to harsh environmental conditi ons and/or to chemically active substrates and products. The residues invol ved in the vanadate binding are conserved between the two algal bromoperoxi dases and the vanadium chloroperoxidase from the fungus Curvularia inaequal is. However, most of the other residues forming the active-site cavity are different in the three enzymes, which reflects differences in the substrate specificity and stereoselectivity of the reaction. A dimer of the Cor. off icinalis enzyme partially superimposes with the two-domain monomer of the f ungal enzyme. (C) 2000 Academic Press.