| 研究実績の概要 |
In order to understand contribution of electrostatic interactions to formation of electron transfer complex and their effects on enzymatic activity, we have conducted thermodynamic studies on binding reactions between ferredoxin (Fd) and sulfite reductase (SiR) as well as Fd and ferredoxin NADP(+)-reductase (FNR) using isothermal titration calorimetry, NMR spectroscopy, and X-ray crystallographic analysis together with FNR and SiR activity assays.
We have revealed that oppositely-charged Fd and SiR formed the electron transfer complex using attractive charge-charge interactions. In addition, non-electrostatic interactions is also important for fine tuning of binding modes between Fd and SiR to optimize SiR activity (Kim et al. (2015) and Kim et al. in preparation). The same results were obtained in the binding system between Fd and FNR (Kinoshita et al. (2015) under peer-review).
Simultaneously, we have investigated the conformational stability of amyloid fibrils of various amyloidogenic proteins/peptides such as alpha-synuclein and amyloid beta peptides in the wide temperature range (273-385K). Although all fibrils heat-denatured over 333K, only amyloid fibrils of alpha-synuclein cold-denatured below 293K due to the repulsive electrostatic interactions at low temperature (Ikenoue and Lee et al. (2014)). Effects of maturation of alpha-synuclein fibrils on stability have been further being examined.
We have clearly demonstrated that interprotein electrostatic interactions play an important roles in normal protein functions and in clearance of disease-related amyloid fibrils.
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