Issue 42, 2021

Functional and protective hole hopping in metalloenzymes

Abstract

Electrons can tunnel through proteins in microseconds with a modest release of free energy over distances in the 15 to 20 Å range. To span greater distances, or to move faster, multiple charge transfers (hops) are required. When one of the reactants is a strong oxidant, it is convenient to consider the movement of a positively charged “hole” in a direction opposite to that of the electron. Hole hopping along chains of tryptophan (Trp) and tyrosine (Tyr) residues is a critical function in several metalloenzymes that generate high-potential intermediates by reactions with O2 or H2O2, or by activation with visible light. Examination of the protein structural database revealed that Tyr/Trp chains are common protein structural elements, particularly among enzymes that react with O2 and H2O2. In many cases these chains may serve a protective role in metalloenzymes by deactivating high-potential reactive intermediates formed in uncoupled catalytic turnover.

Graphical abstract: Functional and protective hole hopping in metalloenzymes

Article information

Article type
Perspective
Submitted
04 Aug 2021
Accepted
20 Sep 2021
First published
27 Sep 2021
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2021,12, 13988-14003

Functional and protective hole hopping in metalloenzymes

H. B. Gray and J. R. Winkler, Chem. Sci., 2021, 12, 13988 DOI: 10.1039/D1SC04286F

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