HORSERADISH PEROXIDASE C*: CRYSTAL STRUCTURE WITH AND WITHOUT THE SUBSTRATE: BENZENE HYDROXAMINE ACID (BHA) BOUND IN THE ACTIVE SITE. M. Gajhede, A. Henriksen, Centre for Crystallographic Studies, Department of Chemistry, The H.C. Orsted Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark, D.J. Schuller, Department of Molecular Biology & Biochemistry, University of California, Irvine California USA & A.T. Smith, Biochemistry Laboratory, School of Biological Sciences, University of Sussex, Brighton BN1 9QG, England

When focusing on Heme-containing proteins, the three-dimensional structure is known for quite a few: A large number of members of the Cytochrome c and Globin-like superfamilies, members of the superfamily of Heme-linked catalases and members from the superfamily of Heme-dependent peroxidases. However there is still one very important class of structures of heme-containing proteins that has been unknown until just recently. This is the class of plant peroxidases. Now however the structures of peanut peroxidase (Schuller D.J., Ban N., van Huystee, R.B., McPherson A. & Poulos T.L. (1996) Structure, in press), barley peroxidase (Henriksen A., Welinder K.G. & Gajhede M. in preparation) and recombinant horseradish peroxidase C (HRPC*) (Gajhede M., Schuller D.J, Henriksen A., Smith A.T. & Poulos T.L. in preparation) have been solved. The structure of HRPC* has been solved by molecular replacement, using the peanut peroxidase structure as a model. The structure has been solved in two crystal forms: with and without the substrate benzene hydroxamine acid bound in the active site. A detailed analysis of the two structures will be presented.