@article {1135,
	title = {Spectroscopic studies of the anaerobic enzyme - Substrate complex of catechol 1,2-dioxygenase},
	journal = {Journal of the American Chemical Society},
	volume = {127},
	number = {48},
	year = {2005},
	note = {ISI Document Delivery No.: 990QVTimes Cited: 17Cited Reference Count: 86},
	month = {Dec},
	pages = {16882-16891},
	type = {Article},
	abstract = {The basis of the respective regiospecificities of intradiol and extradiol dioxygenase is poorly understood and may be linked to the protonation state of the bidentate-bound catechol in the enzyme/ substrate complex. Previous ultraviolet resonance Raman (UVRR) and UV-visible (UV-vis) difference spectroscopic studies demonstrated that, in extradiol dioxygenases, the catechol is bound to the Fe(II) as a monoanion. In this study, we use the same approaches to demonstrate that, in catechol 1,2-dioxygenase (C120), an intradiol enzyme, the catechol binds to the Fe(III) as a dianion. Specifically, features at 290 nm and 1550 cm(-1) in the UV-vis and UVRR difference spectra, respectively, are assigned to dianionic catechol based on spectra of the model compound, ferric tris(catecholate). The UVRR spectroscopic band assignments are corroborated by density functional theory (DFT) calculations. In addition, negative features at 240 nm in UV-vis difference spectra and at 1600, 1210, and 1175 cm(-1) in UVRR difference spectra match those of a tyrosinate model compound, consistent with protonation of the axial tyrosinate ligand when it is displaced from the ferric ion coordination sphere upon substrate binding. The DFT calculations ascribe the asymmetry of the bound dianionic substrate to the trans donor effect of an equatorially ligated tyrosinate ligand. In addition, the computations suggest that trans donation from the tyrosinate ligand may facilitate charge transfer from the substrate to yield the iron-bound semiquinone transition state, which is capable of reacting with dioxygen. In illustrating the importance of ligand trans effects in a biological system, the current study demonstrates the power of combining difference UVRR and optical spectroscopies to probe metal ligation in solution.},
	keywords = {1, 2, 2-DIOXYGENASE, 3-DIHYDROXYBIPHENYL, 4-DIOXYGENASE, ACTIVE-SITE, CRYSTAL-STRUCTURE, DENSITY-FUNCTIONAL THEORY, EXTRADIOL DIOXYGENASES, IRON-TRANSPORT COMPOUNDS, ISOTOPIC-SUBSTITUTION SHIFTS, PROTOCATECHUATE 3, PSEUDOMONAS-ARVILLA C-1, RESONANCE RAMAN-SPECTROSCOPY},
	isbn = {0002-7863},
	url = {<Go to ISI>://000233759200038},
	author = {Horsman, G. P. and Jirasek, A. and Vaillancourt, F. H. and Barbosa, C. J. and Jarzecki, A. A. and Xu, C. L. and Mekmouche, Y. and Spiro, T. G. and Lipscomb, J. D. and Blades, M. W. and Turner, R. F. B. and Eltis, L. D.}
}
@article {1135,
	title = {Spectroscopic studies of the anaerobic enzyme - Substrate complex of catechol 1,2-dioxygenase},
	journal = {Journal of the American Chemical Society},
	volume = {127},
	number = {48},
	year = {2005},
	note = {ISI Document Delivery No.: 990QVTimes Cited: 17Cited Reference Count: 86},
	month = {Dec},
	pages = {16882-16891},
	type = {Article},
	abstract = {The basis of the respective regiospecificities of intradiol and extradiol dioxygenase is poorly understood and may be linked to the protonation state of the bidentate-bound catechol in the enzyme/ substrate complex. Previous ultraviolet resonance Raman (UVRR) and UV-visible (UV-vis) difference spectroscopic studies demonstrated that, in extradiol dioxygenases, the catechol is bound to the Fe(II) as a monoanion. In this study, we use the same approaches to demonstrate that, in catechol 1,2-dioxygenase (C120), an intradiol enzyme, the catechol binds to the Fe(III) as a dianion. Specifically, features at 290 nm and 1550 cm(-1) in the UV-vis and UVRR difference spectra, respectively, are assigned to dianionic catechol based on spectra of the model compound, ferric tris(catecholate). The UVRR spectroscopic band assignments are corroborated by density functional theory (DFT) calculations. In addition, negative features at 240 nm in UV-vis difference spectra and at 1600, 1210, and 1175 cm(-1) in UVRR difference spectra match those of a tyrosinate model compound, consistent with protonation of the axial tyrosinate ligand when it is displaced from the ferric ion coordination sphere upon substrate binding. The DFT calculations ascribe the asymmetry of the bound dianionic substrate to the trans donor effect of an equatorially ligated tyrosinate ligand. In addition, the computations suggest that trans donation from the tyrosinate ligand may facilitate charge transfer from the substrate to yield the iron-bound semiquinone transition state, which is capable of reacting with dioxygen. In illustrating the importance of ligand trans effects in a biological system, the current study demonstrates the power of combining difference UVRR and optical spectroscopies to probe metal ligation in solution.},
	keywords = {1, 2, 2-DIOXYGENASE, 3-DIHYDROXYBIPHENYL, 4-DIOXYGENASE, ACTIVE-SITE, CRYSTAL-STRUCTURE, DENSITY-FUNCTIONAL THEORY, EXTRADIOL DIOXYGENASES, IRON-TRANSPORT COMPOUNDS, ISOTOPIC-SUBSTITUTION SHIFTS, PROTOCATECHUATE 3, PSEUDOMONAS-ARVILLA C-1, RESONANCE RAMAN-SPECTROSCOPY},
	isbn = {0002-7863},
	url = {<Go to ISI>://000233759200038},
	author = {Horsman, G. P. and Jirasek, A. and Vaillancourt, F. H. and Barbosa, C. J. and Jarzecki, A. A. and Xu, C. L. and Mekmouche, Y. and Spiro, T. G. and Lipscomb, J. D. and Blades, M. W. and Turner, R. F. B. and Eltis, L. D.}
}
@article {529,
	title = {Definitive evidence for monoanionic binding of 2,3-dihydroxybiphenyl to 2,3-dihydroxybiphenyl 1,2-dioxygenase from UV resonance Raman spectroscopy, UV/Vis absorption spectroscopy, and crystallography},
	journal = {Journal of the American Chemical Society},
	volume = {124},
	number = {11},
	year = {2002},
	note = {ISI Document Delivery No.: 531UMTimes Cited: 53Cited Reference Count: 79},
	month = {Mar},
	pages = {2485-2496},
	type = {Article},
	abstract = {Ultraviolet resonance Raman spectroscopy (UVRRS), electronic absorption spectroscopy, and X-ray crystallography were used to probe the nature of the binding of 2,3-dihydroxybiphenyl (DHB) to the extradiol ring-cleavage enzyme, 2,3-dihydroxybiphenyl 1,2-dioxygenase (DHBD; EC 1.13.11.39). The lowest lying transitions in the electronic absorption spectrum of DHBD-bound DHB occurred at 299 nm, compared to 305 nm for the monoanionic DHB species in buffer. In contrast, the corresponding transitions in neutral and dianionic DHB occurred at 283 and 348 nm, respectively, indicating that DHBD-bound DHB is monoanionic. These binding-induced spectral changes, and the use of custom-designed optical fiber probes, facilitated UVRR experiments. The strongest feature of the UVRR spectrum of DHB was a Y8a-like mode around 1600 cm(-1), whose position depended strongly on the protonation state of the DHB. In the spectrum of the DHBD-bound species, this feature occurred at 1603 cm-1, as observed in the spectrum of monoanionic DHB. Raman band shifts were observed in deuterated solvent, ruling out dianionic binding of the substrate. Thus, the electronic absorption and UVRRS data demonstrate that DHBD binds its catecholic substrate as a monoanion, definitively establishing this feature of the proposed mechanism of extradiol dioxygenases. This conclusion is supported by a crystal structure of the DHBD:DHB complex at 2.0 Angstrom resolution, which suggests that the substrate{\textquoteright}s 2-hydroxyl substituent, and not the 3-hydroxyl group, deprotonates upon binding. The structural data also show that the aromatic rings of the enzyme-bound DHB are essentially orthogonal to each other. Thus, the 6 nm blue shift of the transition for bound DHB relative to the monoanion in solution could indicate a conformational change upon binding. Catalytic roles of active site residues are proposed based on the structural data and previously proposed mechanistic schemes.},
	keywords = {3, 4-DIOXYGENASE, BIPHENYL, CRYSTAL-STRUCTURE, EXTRADIOL CATECHOL DIOXYGENASES, FE(II) ACTIVE-SITE, FE3+ LIGAND, LIGAND-BINDING, MECHANISM, MOLECULAR-STRUCTURE, PROTOCATECHUATE, SUBSTRATE-BINDING},
	isbn = {0002-7863},
	url = {<Go to ISI>://000174435700037},
	author = {Vaillancourt, F. H. and Barbosa, C. J. and Spiro, T. G. and Bolin, J. T. and Blades, M. W. and Turner, R. F. B. and Eltis, L. D.}
}
@article {529,
	title = {Definitive evidence for monoanionic binding of 2,3-dihydroxybiphenyl to 2,3-dihydroxybiphenyl 1,2-dioxygenase from UV resonance Raman spectroscopy, UV/Vis absorption spectroscopy, and crystallography},
	journal = {Journal of the American Chemical Society},
	volume = {124},
	number = {11},
	year = {2002},
	note = {ISI Document Delivery No.: 531UMTimes Cited: 53Cited Reference Count: 79},
	month = {Mar},
	pages = {2485-2496},
	type = {Article},
	abstract = {Ultraviolet resonance Raman spectroscopy (UVRRS), electronic absorption spectroscopy, and X-ray crystallography were used to probe the nature of the binding of 2,3-dihydroxybiphenyl (DHB) to the extradiol ring-cleavage enzyme, 2,3-dihydroxybiphenyl 1,2-dioxygenase (DHBD; EC 1.13.11.39). The lowest lying transitions in the electronic absorption spectrum of DHBD-bound DHB occurred at 299 nm, compared to 305 nm for the monoanionic DHB species in buffer. In contrast, the corresponding transitions in neutral and dianionic DHB occurred at 283 and 348 nm, respectively, indicating that DHBD-bound DHB is monoanionic. These binding-induced spectral changes, and the use of custom-designed optical fiber probes, facilitated UVRR experiments. The strongest feature of the UVRR spectrum of DHB was a Y8a-like mode around 1600 cm(-1), whose position depended strongly on the protonation state of the DHB. In the spectrum of the DHBD-bound species, this feature occurred at 1603 cm-1, as observed in the spectrum of monoanionic DHB. Raman band shifts were observed in deuterated solvent, ruling out dianionic binding of the substrate. Thus, the electronic absorption and UVRRS data demonstrate that DHBD binds its catecholic substrate as a monoanion, definitively establishing this feature of the proposed mechanism of extradiol dioxygenases. This conclusion is supported by a crystal structure of the DHBD:DHB complex at 2.0 Angstrom resolution, which suggests that the substrate{\textquoteright}s 2-hydroxyl substituent, and not the 3-hydroxyl group, deprotonates upon binding. The structural data also show that the aromatic rings of the enzyme-bound DHB are essentially orthogonal to each other. Thus, the 6 nm blue shift of the transition for bound DHB relative to the monoanion in solution could indicate a conformational change upon binding. Catalytic roles of active site residues are proposed based on the structural data and previously proposed mechanistic schemes.},
	keywords = {3, 4-DIOXYGENASE, BIPHENYL, CRYSTAL-STRUCTURE, EXTRADIOL CATECHOL DIOXYGENASES, FE(II) ACTIVE-SITE, FE3+ LIGAND, LIGAND-BINDING, MECHANISM, MOLECULAR-STRUCTURE, PROTOCATECHUATE, SUBSTRATE-BINDING},
	isbn = {0002-7863},
	url = {<Go to ISI>://000174435700037},
	author = {Vaillancourt, F. H. and Barbosa, C. J. and Spiro, T. G. and Bolin, J. T. and Blades, M. W. and Turner, R. F. B. and Eltis, L. D.}
}
