Download MendeleyOxygen Activation Switch in the Copper Amine Oxidase of Escherichia coli.
Gaule, T.G., Smith, M.A., Tych, K.M., Pirrat, P., Trinh, C.H., Pearson, A.R., Knowles, P.F., McPherson, M.J.(2018) Biochemistry 57: 5301-5314
- PubMed: 30110143
- DOI: https://doi.org/10.1021/acs.biochem.8b00633
- Primary Citation of Related Structures:
6EZZ, 6GRR - PubMed Abstract:
Copper amine oxidases (CuAOs) are metalloenzymes that reduce molecular oxygen to hydrogen peroxide during catalytic turnover of primary amines. In addition to Cu 2+ in the active site, two peripheral calcium sites, ∼32 Å from the active site, have roles in Escherichia coli amine oxidase (ECAO). The buried Ca 2+ (Asp533, Leu534, Asp535, Asp678, and Ala679) is essential for full-length protein production, while the surface Ca 2+ (Glu573, Tyr667, Asp670, and Glu672) modulates biogenesis of the 2,4,5-trihydroxyphenylalanine quinone (TPQ) cofactor. The E573Q mutation at the surface site prevents calcium binding and TPQ biogenesis. However, TPQ biogenesis can be restored by a suppressor mutation (I342F) in the proposed oxygen delivery channel to the active site. While supporting TPQ biogenesis (∼60% WTECAO TPQ), I342F/E573Q has almost no amine oxidase activity (∼4.6% WTECAO activity). To understand how these long-range mutations have major effects on TPQ biogenesis and catalysis, we employed ultraviolet-visible spectroscopy, steady-state kinetics, inhibition assays, and X-ray crystallography. We show that the surface metal site controls the equilibrium (disproportionation) of the Cu 2+ -substrate reduced TPQ (TPQ AMQ ) Cu + -TPQ semiquinone (TPQ SQ ) couple. Removal of the calcium ion from this site by chelation or mutagenesis shifts the equilibrium to Cu 2+ -TPQ AMQ or destabilizes Cu + -TPQ SQ . Crystal structure analysis shows that TPQ biogenesis is stalled at deprotonation in the Cu 2+ -tyrosinate state. Our findings support WTECAO using the inner sphere electron transfer mechanism for oxygen reduction during catalysis, and while a Cu + -tyrosyl radical intermediate is not essential for TPQ biogenesis, it is required for efficient biogenesis.
Organizational Affiliation:
Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences , University of Leeds , Leeds LS2 9JT , U.K.
