Kim, JY, Kinoshita, M, Kume, S et al. (9 more authors) (2016) Non-covalent forces tune the electron transfer complex between ferredoxin and sulfite reductase to optimize enzymatic activity. Biochemical Journal, 473 (21). pp. 3837-3854. ISSN 0264-6021
Abstract
Although electrostatic interactions between negatively-charged ferredoxin (Fd) and positively-charged sulfite reductase (SiR) have been predominantly highlighted to characterize complex formation, the detailed nature of intermolecular forces remains to be fully elucidated. We herein investigated interprotein forces for formation of an electron-transfer complex between Fd and SiR and their relationship to SiR activity using various approaches over NaCl concentrations between 0 and 400 mM. Fd-dependent SiR activity assays revealed a bell-shaped activity curve with a maximum around 40-70 mM NaCl and a reverse bell-shaped dependence of interprotein affinity. Meanwhile, intrinsic SiR activity, as measured in a methyl viologen-dependent assay, exhibited saturation above 100 mM NaCl. Thus, two assays suggested that interprotein interaction is crucial in controlling Fd-dependent SiR activity. Calorimetric analyses showed the monotonic decrease in interprotein affinity on increasing NaCl concentrations, distinguished from a reverse bell-shaped interprotein affinity observed from Fd-dependent SiR activity assay . Furthermore, Fd:SiR complex formation and interprotein affinity were thermodynamically adjusted by both enthalpy and entropy through electrostatic and non-electrostatic interactions. A residue-based NMR investigation on addition of SiR to 15N-labeled Fd at the various NaCl concentration also demonstrated that a combination of electro- and non-electrostatic forces stabilized the complex with similar interfaces and modulated the binding affinity and mode. Our findings elucidate that non-electrostatic forces are also essential for the formation and modulation of the Fd:SiR complex. We suggest that a complex configuration optimized for maximum enzymatic activity near physiological salt conditions is achieved by structural rearrangement through controlled non-covalent interprotein interactions.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2016, The Author(s). Published by Portland Press. This is an author produced version of a paper published in Biochemical Journal. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | Electron transfer complex; enzyme activity; ferredoxin; isothermal titration calorimetry; nuclear magnetic resonance; sulfite reductase |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Biological Sciences (Leeds) > School of Molecular and Cellular Biology (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 09 Sep 2016 14:20 |
Last Modified: | 23 Aug 2017 08:00 |
Published Version: | http://dx.doi.org/10.1042/BCJ20160658 |
Status: | Published |
Publisher: | Portland Press |
Identification Number: | 10.1042/BCJ20160658 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:104525 |