A Structural Model for the Galactose Oxidase Active Site which Shows Counteranion-Dependent Phenoxyl Radical Formation by Disproportionation

2000 ◽  
Vol 39 (9) ◽  
pp. 1666-1669 ◽  
Author(s):  
Yuichi Shimazaki ◽  
Stefan Huth ◽  
Akira Odani ◽  
Osamu Yamauchi
Keyword(s):  
Active Site ◽  
Structural Model ◽  
Phenoxyl Radical ◽  
Radical Formation ◽  
Galactose Oxidase

Strongly Coupled Redox-Linked Conformational Switching at the Active Site of the Non-Heme Iron-Dependent Dioxygenase, TauD

2019 ◽  
Author(s):  
Christopher John ◽  
Greg M. Swain ◽  
Robert P. Hausinger ◽  
Denis A. Proshlyakov
Keyword(s):  
Active Site ◽  
Structural Model ◽  
Heme Iron ◽  
Chemical Transformations ◽  
Experimental Conditions ◽  
Strongly Coupled ◽  
Non Heme Iron ◽  
Reversible Redox ◽  
Wide Range ◽  
Complex Structural

2-Oxoglutarate (2OG)-dependent dioxygenases catalyze C-H activation while performing a wide range of chemical transformations. In contrast to their heme analogues, non-heme iron centers afford greater structural flexibility with important implications for their diverse catalytic mechanisms. We characterize an <i>in situ</i> structural model of the putative transient ferric intermediate of 2OG:taurine dioxygenase (TauD) by using a combination of spectroelectrochemical and semi-empirical computational methods, demonstrating that the Fe (III/II) transition involves a substantial, fully reversible, redox-linked conformational change at the active site. This rearrangement alters the apparent redox potential of the active site between -127 mV for reduction of the ferric state and 171 mV for oxidation of the ferrous state of the 2OG-Fe-TauD complex. Structural perturbations exhibit limited sensitivity to mediator concentrations and potential pulse duration. Similar changes were observed in the Fe-TauD and taurine-2OG-Fe-TauD complexes, thus attributing the reorganization to the protein moiety rather than the cosubstrates. Redox difference infrared spectra indicate a reorganization of the protein backbone in addition to the involvement of carboxylate and histidine ligands. Quantitative modeling of the transient redox response using two alternative reaction schemes across a variety of experimental conditions strongly supports the proposal for intrinsic protein reorganization as the origin of the experimental observations.

Spectroscopic and magnetochemical studies on the active site copper complex in galactose oxidase

2000 ◽  
Vol 8 (1-3) ◽  
pp. 3-15 ◽  
Author(s):  
Mei M. Whittaker ◽  
Christopher A. Ekberg ◽  
James Peterson ◽  
Mariana S. Sendova ◽  
Edmund P. Day ◽  
...  
Keyword(s):  
Copper Complex ◽  
Active Site ◽  
Galactose Oxidase

scholarly journals Solution studies of copper(II) complexes as a contribution to the study of the active site of galactose oxidase

2004 ◽  
Vol 15 (6) ◽  
pp. 897-903 ◽  
Author(s):  
Stela Maris de M. Romanowski ◽  
Francielen Tormena ◽  
Viviane A. dos Santos ◽  
Monique de F. Hermann ◽  
Antonio S. Mangrich
Keyword(s):  
Active Site ◽  
Galactose Oxidase ◽  
Solution Studies

scholarly journals Mutations in the Predicted Active Site of Xanthomonas oryzae pv. oryzae XopQ Differentially Affect Virulence, Suppression of Host Innate Immunity, and Induction of the HR in a Nonhost Plant

2015 ◽  
Vol 28 (2) ◽  
pp. 195-206 ◽  
Author(s):  
Mahesh Kumar Gupta ◽  
Rajkanwar Nathawat ◽  
Dipanwita Sinha ◽  
Asfarul S. Haque ◽  
Rajan Sankaranarayanan ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Active Site ◽  
Plant Cell Wall ◽  
Structural Model ◽  
Bioinformatic Analysis ◽  
Xanthomonas Oryzae ◽  
Active Site Residues ◽  
Callose Deposition ◽  
Nonhost Plant ◽  
Bacterial Blight Pathogen

Xanthomonas oryzae pv. oryzae, the bacterial blight pathogen of rice, secretes a number of effectors through a type 3 secretion system. One of these effectors, called XopQ, is required for virulence and suppression of rice innate immune responses induced by the plant cell-wall-degrading enzyme lipase/esterase A (LipA). Bioinformatic analysis suggested that XopQ is homologous to inosine-uridine nucleoside hydrolases (NH). A structural model of XopQ with the protozoan Crithidia fasciculata purine NH suggested that D116 and Y279 are potential active site residues. X. oryzae pv. oryzae xopQ mutants (xopQ−/pHM1::xopQD116A and xopQ−/pHM1::xopQY279A) show reduced virulence on rice compared with xopQ−/pHM1::xopQ. The two predicted XopQ active site mutants (xopQ−/pHM1::xopQD116A and xopQ−/pHM1::xopQY279A) exhibit a reduced hypersensitive response (HR) on Nicotiana benthamiana, a nonhost. However, Arabidopsis lines expressing either xopQ or xopQY279A are equally proficient at suppression of LipA-induced callose deposition. Purified XopQ does not show NH activity on standard nucleoside substrates but exhibits ribose hydrolase activity on the nucleoside substrate analogue 4-nitrophenyl β-D-ribofuranoside. The D116A and Y279A mutations cause a reduction in biochemical activity. These results indicate that mutations in the predicted active site of XopQ affect virulence and induction of the HR but do not affect suppression of innate immunity.

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