The radical site in chlamydial ribonucleotide reductase defines a new R2 subclass.
Ribonucleotide reductase (RNR) synthesizes the deoxyribonucleotides for DNA synthesis. The R2 protein of normal class I ribonucleotide reductases contains a diiron site that produces a stable tyrosyl free radical, essential for enzymatic activity. Structural and electron paramagnetic resonance studies of R2 from Chlamydia trachomatis reveal a protein lacking a tyrosyl radical site. Instead, the protein yields an iron-coupled radical upon reconstitution. The coordinating structure of the diiron site is similar to that of diiron oxidases/monoxygenases and supports a role for this radical in the RNR mechanism. The specific ligand pattern in the C. trachomatis R2 metal site characterizes a new group of R2 proteins that so far has been found in eight organisms, three of which are human pathogens.
Högbom
Martin
M
Department of Biochemistry and Biophysics, Stockholm University, Roslagstullsbacken 15, Albanova University Center, SE-10691 Stockholm, Sweden.
Stenmark
Pål
P
Voevodskaya
Nina
N
McClarty
Grant
G
Gräslund
Astrid
A
Nordlund
Pär
P
D000595:Amino Acid Sequence; D002692:Chlamydia trachomatis / Q000201:enzymology*; D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D006860:Hydrogen Bonding; D007501:Iron / Q000032:analysis; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D017510:Protein Folding; D017433:Protein Structure, Secondary; D012264:Ribonucleotide Reductases / Q000737:chemistry* / Q000145:classification / Q000378:metabolism; D014443:Tyrosine / Q000032:analysis
D005609:Free Radicals; D008024:Ligands; D014443:Tyrosine; D007501:Iron; D012264:Ribonucleotide Reductases; C108427:ribonucleotide reductase R2 subunit; D010100:Oxygen