title: 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.
authors: Institute for Protein Research, Osaka University, Japan Science and Technology Agency, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors: Young-Ho
authors: YH
authors: Lee
authors: Takahisa
authors: T
authors: Ikegami
authors: Daron M
authors: DM
authors: Standley
authors: Kazumasa
authors: K
authors: Sakurai
authors: Toshiharu
authors: T
authors: Hase
authors: Yuji
authors: Y
authors: Goto
mesh_terms: D019277:Entropy; D005287:Ferredoxin-NADP Reductase / Q000737:chemistry* / Q000378:metabolism*; D005288:Ferredoxins / Q000737:chemistry* / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D011485:Protein Binding; D013329:Structure-Activity Relationship
chemical_list: D005288:Ferredoxins; D005287:Ferredoxin-NADP Reductase