Structure of the Reduced Copper Active Site in Preprocessed Galactose Oxidase: Ligand Tuning for One-Electron O 2 Activation in Cofactor Biogenesis.

Autor: Cowley RE; Department of Chemistry, Stanford University , Stanford, California 94305, United States., Cirera J; Department of Chemistry, Stanford University , Stanford, California 94305, United States., Qayyum MF; Department of Chemistry, Stanford University , Stanford, California 94305, United States., Rokhsana D; Department of Chemistry and Biochemistry, Montana State University , Bozeman, Montana 59717, United States., Hedman B; Department of Chemistry, Stanford University , Stanford, California 94305, United States.; Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University , Menlo Park, California 94025, United States., Hodgson KO; Department of Chemistry, Stanford University , Stanford, California 94305, United States.; Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University , Menlo Park, California 94025, United States., Dooley DM; Department of Chemistry and Biochemistry, Montana State University , Bozeman, Montana 59717, United States.; University of Rhode Island , Kingston, Rhode Island 02881, United States., Solomon EI; Department of Chemistry, Stanford University , Stanford, California 94305, United States.; Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University , Menlo Park, California 94025, United States.
Jazyk: angličtina
Zdroj: Journal of the American Chemical Society [J Am Chem Soc] 2016 Oct 12; Vol. 138 (40), pp. 13219-13229. Date of Electronic Publication: 2016 Sep 28.
DOI: 10.1021/jacs.6b05792
Abstrakt: Galactose oxidase (GO) is a copper-dependent enzyme that accomplishes 2e - substrate oxidation by pairing a single copper with an unusual cysteinylated tyrosine (Cys-Tyr) redox cofactor. Previous studies have demonstrated that the post-translational biogenesis of Cys-Tyr is copper- and O 2 -dependent, resulting in a self-processing enzyme system. To investigate the mechanism of cofactor biogenesis in GO, the active-site structure of Cu(I)-loaded GO was determined using X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy, and density-functional theory (DFT) calculations were performed on this model. Our results show that the active-site tyrosine lowers the Cu potential to enable the thermodynamically unfavorable 1e - reduction of O 2 , and the resulting Cu(II)-O 2 •- is activated toward H atom abstraction from cysteine. The final step of biogenesis is a concerted reaction involving coordinated Tyr ring deprotonation where Cu(II) coordination enables formation of the Cys-Tyr cross-link. These spectroscopic and computational results highlight the role of the Cu(I) in enabling O 2 activation by 1e - and the role of the resulting Cu(II) in enabling substrate activation for biogenesis.
Databáze: MEDLINE
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