2 publications

2 publications

Construction of a Hybrid Biocatalyst Containing a Covalently-Linked Terpyridine Metal Complex within a Cavity of Aponitrobindin

Onoda, A.

J. Inorg. Biochem. 2016, 158, 55-61, 10.1016/j.jinorgbio.2015.12.026

A hybrid biocatalyst containing a metal terpyridine (tpy) complex within a rigid β-barrel protein nitrobindin (NB) is constructed. A tpy ligand with a maleimide group, N-[2-([2,2′:6′,2′′-terpyridin]-4′-yloxy)ethyl]maleimide (1), was covalently linked to Cys96 inside the cavity of NB to prepare a conjugate NB–1. Binding of Cu2 +, Zn2 +, or Co2 + ion to the tpy ligand in NB–1 was confirmed by UV–vis spectroscopy and ESI–TOF MS measurements. Cu2 +-bound NB–1 is found to catalyze a Diels–Alder reaction between azachalcone and cyclopentadiene in 22% yield, which is higher than that of the Cu2 +–tpy complex without the NB matrix. The results suggest that the hydrophobic cavity close to the copper active site within the NB scaffold supports the binding of the two substrates, dienophile and diene, to promote the reaction.


Metal: Cu
Ligand type: Terpyridine
Host protein: Nitrobindin (Nb)
Anchoring strategy: Cystein-maleimide
Optimization: ---
Max TON: ---
ee: ---
PDB: ---
Notes: ---

Photoinduced Electron Transfer within Supramolecular Hemoprotein Co-Assemblies and Heterodimers Containing Fe and Zn Porphyrins

Oohora, K.

J. Inorg. Biochem. 2019, 193, 42-51, 10.1016/j.jinorgbio.2019.01.001

Electron transfer (ET) events occurring within metalloprotein complexes are among the most important classes of reactions in biological systems. This report describes a photoinduced electron transfer between Zn porphyrin and Fe porphyrin within a supramolecular cytochrome b562 (Cyt b562) co-assembly or heterodimer with a well-defined rigid structure formed by a metalloporphyrin–heme pocket interaction and a hydrogen-bond network at the protein interface. The photoinduced charge separation (CS: kCS = 320–600 s−1) and subsequent charge recombination (CR: kCR = 580–930 s−1) were observed in both the Cyt b562 co-assembly and the heterodimer. In contrast, interestingly, no ET events were observed in a system comprised of a flexible and structurally-undefined co-assembly and heterodimers which lack the key hydrogen-bond interaction at the protein interface. Moreover, analysis of the kinetic constants of CS and CR of the heterodimer using the Marcus equation suggests that a single-step ET reaction occurs in the system. These findings provide strong support that the rigid hemoprotein-assembling system containing an appropriate hydrogen-bond network at the protein interface is essential for monitoring the ET reaction.


Metal: Fe; Zn
Ligand type: Protoporphyrin IX
Host protein: Cytochrome b562
Anchoring strategy: Cystein-maleimide; Supramolecular
Optimization: Chemical & genetic
Reaction: Electron transfer
Max TON: ---
ee: ---
PDB: ---
Notes: ---