Question about flavodiiron protein I came across an article about flavodiiron proteins that are responsible for reducing ${\rm O}_2$ to ${\rm H}_2{\rm O}$ thereby protecting the anaerobic prokaryotes and some eukaryot...--prophetes.ai

Question about flavodiiron protein I came across an article about flavodiiron proteins that are responsible for reducing ${\rm O}_2$ to ${\rm H}_2{\rm O}$ thereby protecting the anaerobic prokaryotes and some eukaryotes from oxidative stress. However, I am confused about the structure of that protein and its relation to heme proteins. Is this a heme protein? The article I am reading is: > Di Matteo _et al._ , The O2-scavenging flavodiiron protein in the human parasite Giardia intestinalis. J Biol Chem. 2008 Feb 15;283(7):4061-8. Epub 2007 Dec 12.

No flavodiiron proteins are not haem proteins. See here for a simple depiction. Basically there is a flavin, and there are two iron atoms which go through a FeII/FeIII cycle during catalytic activity. These iron atoms are not held in haem, but rather via carboxylate ligands.