Crystal Structures of the Copper-Containing Amine Oxidase from Arthrobacter globiformis in the Holo and Apo Forms:  Implications for the Biogenesis of Topaquinone

• Published in: Biochemistry (Easton) 1997-12, Vol.36 (51), p.16116-16133
• Main Authors: Wilce, Matthew C. J, Dooley, David M, Freeman, Hans C, Guss, J. Mitchell, Matsunami, Hideyuki, McIntire, William S, Ruggiero, Christy E, Tanizawa, Katsuyuki, Yamaguchi, Hiroshi
• Format: Article
• Language: English
• Subjects: Amine Oxidase (Copper-Containing) - chemistry; Amine Oxidase (Copper-Containing) - metabolism; Amino Acid Sequence; Apoenzymes - chemistry; Arthrobacter - enzymology; Binding Sites; Copper - chemistry; Copper - metabolism; Crystallography, X-Ray; Dihydroxyphenylalanine - analogs & derivatives; Dihydroxyphenylalanine - biosynthesis; Dimerization; Hydrogen Bonding; Metalloproteins - chemistry; Molecular Sequence Data; Protein Conformation; Protein Processing, Post-Translational - physiology; Sequence Alignment; Substrate Specificity; Tyrosine - chemistry; Tyrosine - metabolism
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi971797i

The crystal structures of the copper enzyme phenylethylamine oxidase from the Gram-positive bacterium Arthrobacter globiformis (AGAO) have been determined and refined for three forms of the enzyme:  the holoenzyme in its active form (at 2.2 Å resolution), the holoenzyme in an inactive form (at 2.8 Å resolution), and the apoenzyme (at 2.2 Å resolution). The holoenzyme has a topaquinone (TPQ) cofactor formed from the apoenzyme by the post-translational modification of a tyrosine residue in the presence of Cu2+. Significant differences between the three forms of AGAO are limited to the active site. The polypeptide fold is closely similar to those of the amine oxidases from Escherichia coli [Parsons, M. R., et al. (1995) Structure 3, 1171−1184] and pea seedlings [Kumar, V., et al. (1996) Structure 4, 943−955]. In the active form of holo-AGAO, the active-site Cu atom is coordinated by three His residues and two water molecules in an approximately square-pyramidal arrangement. In the inactive form, the Cu atom is coordinated by the same three His residues and by the phenolic oxygen of the TPQ, the geometry being quasi-trigonal-pyramidal. There is evidence of disorder in the crystals of both forms of holo-AGAO. As a result, only the position of the aromatic group of the TPQ cofactor, but not its orientation about the Cβ−Cγ bond, is determined unequivocally. In apo-AGAO, electron density consistent with an unmodified Tyr occurs at a position close to that of the TPQ in the inactive holo-AGAO. This observation has implications for the biogenesis of TPQ. Two features which have not been described previously in amine oxidase structures are a channel from the molecular surface to the active site and a solvent-filled cavity at the major interface between the two subunits of the dimer.