ANALYSIS OF THE VANADIUM DEPENDENT HALOPEROXIDASE FROM CORALLINA OFFICINALIS Andrew Dalby¹, Cliff Rush¹, Andrew Willetts¹, Gideon Davies², Zbigniew Dauter³, Jennifer Littlechild¹, ¹Departments of Chemistry and Biological Science, University of Exeter UK., ²Department of Chemistry, University of York, UK., ³EMBL, DESY, Germany.

Crystals have been grown of the vanadium dependent haloperoxidase from Corallina officinalis. The protein is a dodecamer with a subunit mass of 64 kdaltons. Electron microscopy of the similar enzyme from Corallina pilulifera has suggested that it is composed of two stacked hexamers. The enzyme contains no haem and is dependent on vanadium for activity and is particularly thermostable and resistant to organic solvents. It therefore has useful applications in bio-transformations.

Crystals were grown from polyethylene glycol (PEG) 6,000 and 0.4 M potassium chloride by vapour diffusion. Data was collected at the EMBL Hamburg outstation on beamline X11 at a wavelength of 0.92 Å. The crystals diffract beyond 2.0 Å. A data set has been collected to 3.15 Å that is 98 % complete and with an R-merge of 6.5%.

The cell parameters are cubic with a = b = c = 310 Å, and the space group is either I23 or I2₁3. This would infer that there are eight molecules per asymmetric unit with a Matthews coefficient of 2.3 ų/dalton.

With so many molecules in the asymmetric unit the determination of this structure will involve the use of ncs averaging. Currently further native data to higher resolution is being collected.