The histidine brace: nature's copper alternative to haem?

The copper histidine brace is a structural unit in metalloproteins (Proc Natl Acad Sci USA 2011, 108, 15079). It consists of a copper ion chelated by the NH2 and pi-N atom of an N-terminal histidine, and the tau-N atom of a further histidine, in an overall T-shaped coordination geometry (Nat Catal 2018, 1, 571). Like haem-containing proteins, histidine-brace-containing proteins have peroxygenase and/or oxygenase activity, where the substrates are notable for resistance to oxidation, for example, lytic polysaccharide monooxygenases (LPMOs). Moreover, the histidine brace is an invariant unit around which different protein structures exert different activities. Given the similarities in the diversity of function of proteins that contain either the copper histidine brace or haem, the question arises as to whether the functions of histidine brace-containing proteins duplicate those containing haem groups.

Automated summary

The copper histidine brace is a structural unit in metalloproteins that consists of a copper ion chelated by the NH2 and pi-N atom of an N-terminal histidine, and the tau-N atom of a further histidine in T-shaped coordination geometry. Proteins containing the histidine brace exhibit peroxygenase and/or oxygenase activity, similar to haem-containing proteins. The question of whether the functions of histidine brace-containing proteins duplicate those containing haem groups arises due to the similarities in their diversity of function.