Binding energetics of ferredoxin-NADP+ reductase with ferredoxin and its relation to function.
ABSTRACT To obtain insight into the motional features of proteins for enzymatic function, we studied binding reactions between ferredoxin-NADP(+) reductase (FNR) and ferredoxin (Fd) using isothermal titration calorimetry and NMR-based magnetic relaxation and hydrogen/deuterium exchange (HD(ex)). Fd-FNR binding was accompanied by endothermic reactions and driven by the entropy gain. Component-wise analysis of the net entropy change revealed that increases in the conformational entropy of the Fd-FNR complex contributed largely to stabilizing the complex. Intriguingly, analyses of magnetic relaxation and HD(ex) rates with X-ray B factor implied that Fd binding led to both structural stiffening and softening of FNR. Enhanced FNR backbone fluctuations suggest favorable contributions to the net conformational entropy. Fd-bound FNR further showed that relatively large-scale motions of the C terminus, a gatekeeper for interactions of NADP(+) (H), were quenched in the closed form, thereby facilitating exit of NADP(+) (H). This can provide a first dynamic structure-based explanation for the negative cooperativity between Fd and NADP(+) (H) via FNR.
- SourceAvailable from: Antonija KuzmanicJournal of Chemical Theory and Computation 06/2012; 8(10):3820-3829. · 5.31 Impact Factor
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ABSTRACT: The hydrophobic cavity of lipocalin-type prostaglandin D synthase (L-PGDS) has been suggested to accommodate various lipophilic ligands through hydrophobic effects, but its energetic origin remains unknown. We characterized 18 buffer-independent binding systems between human L-PGDS and lipophilic ligands using isothermal titration calorimetry. Although the classical hydrophobic effect was mostly detected, all complex formations were driven by favorable enthalpic gains. Gibbs energy changes strongly correlated with the number of hydrogen bond acceptors of ligand. Thus, the broad binding capability of L-PGDS for ligands should be viewed as hydrophilic interactions delicately tuned by enthalpy-entropy compensation using combined effects of hydrophilic and hydrophobic interactions.FEBS letters 02/2014; · 3.54 Impact Factor
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ABSTRACT: Rapid responses of chloroplast metabolism and adjustments to photosynthetic machinery are of utmost importance for plants' survival in a fluctuating environment. These changes may be achieved through post-translational modifications of proteins, which are known to affect the activity, interactions and localization of proteins. Recent studies have accumulated evidence about the crucial role of a multitude of modifications, including acetylation, methylation and glycosylation, in the regulation of chloroplast proteins. Both of the Arabidopsis (Arabidopsis thaliana) leaf-type ferredoxin-NADP(+) oxidoreductase (FNR) isoforms, the key enzymes linking the light reactions of photosynthesis to carbon assimilation, exist as two distinct forms with different isoelectric points. We show that both At FNR isoforms contain multiple alternative N-termini, and undergo light-responsive N(α)-acetylation that causes the change in pI. Both isoforms were also found to contain acetylation of a conserved lysine residue near the active site, while no evidence for in vivo phosphorylation or glycosylation was detected. The dynamic, multilayer regulation of At FNR exemplifies the complex regulatory network systems controlling chloroplast proteins by a range of PTMs, which continues to emerge as a novel area within photosynthesis research.Plant physiology 10/2014; · 7.39 Impact Factor