scholarly journals Direct Electrochemical Analyses of a Thermophilic Thioredoxin Reductase: Interplay between Conformational Change and Redox Chemistry†

Biochemistry ◽  
2008 ◽  
Vol 47 (37) ◽  
pp. 9738-9746 ◽  
Author(s):  
Michael J. Hamill ◽  
Sarah E. Chobot ◽  
Hector H. Hernandez ◽  
Catherine L. Drennan ◽  
Sean J. Elliott
Keyword(s):  
Conformational Change ◽  
Thioredoxin Reductase ◽  
Redox Chemistry ◽  
Electrochemical Analyses

Conformational Change of Arabidopsis thaliana Thioredoxin Reductase after Binding of Pyridine Nucleotide and Thioredoxin

2001 ◽  
Vol 56 (3-4) ◽  
pp. 188-192
Author(s):  
Henrikas Nivinskas ◽  
Jean-Pierre Jacquot ◽  
Narimantas Čėnas
Keyword(s):  
Arabidopsis Thaliana ◽  
Binding Site ◽  
Conformational Change ◽  
Fluorescence Intensity ◽  
Thioredoxin Reductase ◽  
Pyridine Nucleotide

Abstract We have found that the binding of NADP+ (Kd = 0.86 ±0.11 μᴍ) enhanced the FAD fluorescence of Arabidopsis thaliana NADPH :thioredoxin reductase (TR, EC 1.6.4.5) by 2 times, whereas the binding of 3-aminopyridine adenine dinucleotide phosphate (AADP+) (Kd < 0.1 μᴍ) quenched the fluorescence by 20%. Thioredoxin (TRX) also enhanced the FAD fluorescence by 35%. The Kd of TR-NADP+ and TR-AADP+ complexes did not change in the presence of 45 μᴍ TRX. Our findings imply that the binding of NADP+ and AADP+ at the NADP(H)-binding site of A. thaliana TR, and/or the binding of TRX in the vicinity of the catalytic disulfide increase the content of fluorescent FR conformer (NADP(H)-binding site adjacent to flavin). The different effects of NADP+ and AADP+ on FAD fluorescence intensity may be explained by the superposition of two opposite factors: i) increased content of fluorescent FR conformer upon binding of NADP+ or AADP+; ii) quenching of FAD fluorescence by electron-donating 3-aminopyridinium ring of A ADP+.

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