Crystal structures of the copper-containing amine oxidase from Arthrobacter globiformis in the holo and apo forms: implications for the biogenesis of topaquinone.
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 A resolution), the holoenzyme in an inactive form (at 2.8 A resolution), and the apoenzyme (at 2.2 A 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 Cbeta-Cgamma 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.
Wilce
M C
MC
School of Chemistry and Department of Biochemistry, University of Sydney, New South Wales 2006, Australia.
Dooley
D M
DM
Freeman
H C
HC
Guss
J M
JM
Matsunami
H
H
McIntire
W S
WS
Ruggiero
C E
CE
Tanizawa
K
K
Yamaguchi
H
H
D006631:Amine Oxidase (Copper-Containing) / Q000737:chemistry* / Q000378:metabolism; D000595:Amino Acid Sequence; D001051:Apoenzymes / Q000737:chemistry; D001173:Arthrobacter / Q000201:enzymology*; D001665:Binding Sites; D003300:Copper / Q000737:chemistry / Q000378:metabolism; D018360:Crystallography, X-Ray; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives* / Q000096:biosynthesis; D019281:Dimerization; D006860:Hydrogen Bonding; D008667:Metalloproteins / Q000737:chemistry; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational / Q000502:physiology; D016415:Sequence Alignment; D013379:Substrate Specificity; D014443:Tyrosine / Q000737:chemistry / Q000378:metabolism
D001051:Apoenzymes; D008667:Metalloproteins; D014443:Tyrosine; D004295:Dihydroxyphenylalanine; C067626:6-hydroxydopa quinone; D003300:Copper; C086534:phenylethylamine oxidase; D006631:Amine Oxidase (Copper-Containing)