A stable FeIII-FeIV replacement of tyrosyl radical in a class I ribonucleotide reductase.
Ribonucleotide reductase (RNR) of Chlamydia trachomatis is a class I RNR enzyme composed of two homodimeric components, proteins R1 and R2. In class I RNR, R1 has the substrate binding site, whereas R2 has a diferric site and normally in its active form a stable tyrosyl free radical. C. trachomatis RNR is unusual, because its R2 component has a phenylalanine in the place of the radical carrier tyrosine. Replacing the tyrosyl radical, a paramagnetic Fe(III)-Fe(IV) species (species X, normally a transient intermediate in the process leading to radical formation) may provide the oxidation equivalent needed to start the catalytic process via long range electron transfer from the active site in R1. Here EPR spectroscopy shows that in C. trachomatis RNR, species X can become essentially stable when formed in a complete RNR (R1/R2/substrate) complex, adding further weight to the possible role of this species X in the catalytic reaction.
Voevodskaya
N
N
Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden.
Lendzian
F
F
Gräslund
A
A
D002692:Chlamydia trachomatis / Q000201:enzymology; D004578:Electron Spin Resonance Spectroscopy; D007501:Iron / Q000737:chemistry*; D010084:Oxidation-Reduction; D010649:Phenylalanine / Q000737:chemistry; D011485:Protein Binding; D012264:Ribonucleotide Reductases / Q000737:chemistry*; D014443:Tyrosine / Q000737:chemistry
D014443:Tyrosine; D010649:Phenylalanine; D007501:Iron; D012264:Ribonucleotide Reductases