Crystallographic Study of Yeast Copper Amine Oxidase

The copper‐containing amine oxidase from the yeast Hansenula polymorpha (YAO) has been crystallized and partially solved by molecular replacement. It catalyzes the oxidative deamination of primary amines by molecular oxygen to the corresponding aldehydes, ammonia and hydrogen peroxide. It contains a covalently bound redox cofactor, topa quinone, generated by post‐translational modification of a single tyrosine side chain. The crystals of YAO are orthorhombic, with space‐group symmetry P212121 and unit‐cell dimensions a = 138.8, b = 148.2, c = 234.0 Å and diffract X‐rays beyond 2.0 Å resolution. Solution by molecular replacement using the E. coli amine oxidase structure [Parsons, Convery, Wilmot, Yadav, Blakeley, Corner, Philips, McPherson & Knowles (1995). Structure, 3, 1171–1184] as a search model reveals that there are three dimers in the asymmetric unit in a trigonal arrangement having 32 point‐group symmetry. The solution agrees well with the self‐rotation function of YAO. The non‐crystallographic threefold axis lies parallel to a crystallographic twofold screw axis and each dimer has twofold symmetry. Phases from the refined model based on the molecular‐replacement solution were used to solve one heavy‐atom derivative. Model building from the unbiased isomorphous replacement phases is in progress.