Metal-free class Ie ribonucleotide reductase from pathogens initiates catalysis with a tyrosine-derived dihydroxyphenylalanine radical.
All cells obtain 2'-deoxyribonucleotides for DNA synthesis through the activity of a ribonucleotide reductase (RNR). The class I RNRs found in humans and pathogenic bacteria differ in (i) use of Fe(II), Mn(II), or both for activation of the dinuclear-metallocofactor subunit, β; (ii) reaction of the reduced dimetal center with dioxygen or superoxide for this activation; (iii) requirement (or lack thereof) for a flavoprotein activase, NrdI, to provide the superoxide from O2; and (iv) use of either a stable tyrosyl radical or a high-valent dimetal cluster to initiate each turnover by oxidizing a cysteine residue in the α subunit to a radical (Cys•). The use of manganese by bacterial class I, subclass b-d RNRs, which contrasts with the exclusive use of iron by the eukaryotic Ia enzymes, appears to be a countermeasure of certain pathogens against iron deprivation imposed by their hosts. Here, we report a metal-free type of class I RNR (subclass e) from two human pathogens. The Cys• in its α subunit is generated by a stable, tyrosine-derived dihydroxyphenylalanine radical (DOPA•) in β. The three-electron oxidation producing DOPA• occurs in Escherichia coli only if the β is coexpressed with the NrdI activase encoded adjacently in the pathogen genome. The independence of this new RNR from transition metals, or the requirement for a single metal ion only transiently for activation, may afford the pathogens an even more potent countermeasure against transition metal-directed innate immunity.
['Blaesi|Elizabeth J|EJ|', 'Palowitch|Gavin M|GM|', 'Hu|Kai|K|', 'Kim|Amelia J|AJ|', 'Rose|Hannah R|HR|', 'Alapati|Rahul|R|', 'Lougee|Marshall G|MG|', 'Kim|Hee Jong|HJ|', 'Taguchi|Alexander T|AT|', 'Tan|Kong Ooi|KO|', 'Laremore|Tatiana N|TN|', 'Griffin|Robert G|RG|', 'Krebs|Carsten|C|0000-0002-3302-7053', 'Matthews|Megan L|ML|', 'Silakov|Alexey|A|', 'Bollinger|J Martin|JM|', 'Allen|Benjamin D|BD|', 'Boal|Amie K|AK|']
D004295:Dihydroxyphenylalanine D004926:Escherichia coli D029968:Escherichia coli Proteins D005609:Free Radicals D012264:Ribonucleotide Reductases D014443:Tyrosine
DNA biosynthesis DOPA semiquinone