Radical formation in the dimeric small subunit of ribonucleotide reductase requires only one tyrosine 122.
The small subunit of ribonucleoside-diphosphate reductase (EC 1.17.4.1) is a homodimer. Its catalytic site contains one tyrosyl radical, which is localized to Tyr-122 in one of its polypeptide chains. The engineered Tyr-122----Phe protein was used to demonstrate that it is possible to form a correct ferric iron center in vitro in the absence of Tyr-122. Heterodimers, consisting of one Tyr-122-containing polypeptide chain and one Phe-122-containing polypeptide chain, were constructed. The heterodimer population contained one-half the amount of tyrosyl radical as compared to a homodimer with Tyr-122, i.e. every second heterodimer contains a tyrosyl radical. Thus, one Tyr-122 is sufficient for radical formation. Radical-containing heterodimers are catalytically competent.
D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000201:enzymology; D005609:Free Radicals; D046911:Macromolecular Substances; D011487:Protein Conformation; D012264:Ribonucleotide Reductases / Q000302:isolation & purification / Q000378:metabolism*; D014443:Tyrosine
D005609:Free Radicals; D046911:Macromolecular Substances; D014443:Tyrosine; D012264:Ribonucleotide Reductases