Roelfes, G.

Angew. Chem. Int. Ed. 2018, 57, 7785-7789, 10.1002/anie.201802946

An artificial heme enzyme was created through self‐assembly from hemin and the lactococcal multidrug resistance regulator (LmrR). The crystal structure shows the heme bound inside the hydrophobic pore of the protein, where it appears inaccessible for substrates. However, good catalytic activity and moderate enantioselectivity was observed in an abiological cyclopropanation reaction. We propose that the dynamic nature of the structure of the LmrR protein is key to the observed activity. This was supported by molecular dynamics simulations, which showed transient formation of opened conformations that allow the binding of substrates and the formation of pre‐catalytic structures.

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.

Lin, Y.-W.

ACS Catal. 2020, 10, 14359-14365, 10.1021/acscatal.0c04572

Design of artificial nucleases is essential in biotechnology and biomedicine, whereas few artificial nucleases can both cleave and degrade DNA molecules. Heme proteins are potential enzymes for DNA cleavage. Using a small heme protein, myoglobin (Mb), as a model protein, we engineered a metal-binding motif of [1-His-1-Glu] (native His64 and mutated Glu29) in the heme distal site. The single mutant of L29E Mb was capable of not only efficient DNA cleavage but also DNA degradation upon Mg2+ binding to the heme distal site, as shown by an X-ray crystal structure of the Mg2+-L29E Mb complex. Molecular docking of the protein–DNA complex revealed multiple hydrogen-bonding interactions at their interfaces, involving both minor and major grooves of DNA. Moreover, both the distal Arg45 and the ligand Glu29 were identified as critical residues for the nuclease activity. This study reports the structure of a water-bridged heterodinuclear center of Mg-heme (Mg2+-H2O-Fe3+), showing a similar function as the homodinuclear center (MgA2+-H2O–MgB2+) in natural nuclease, which indicates that the Mg2+-L29E Mb complex is an effective artificial nuclease.