Eklund H, Eriksson M, Uhlin U, Nordlund P, Logan D
Department of Molecular Biology, Swedish University of Agricultural Sciences, Uppsala Biomedical Center, Sweden.
Biol Chem. 1997 Aug;378(8):821-5.
Ribonucleotide reductase contains a stable organic free radical essential for its activity located on a tyrosine residue in the small subunit of the enzyme called R2. The substrate binding site is, however, found in the catalytic subunit called R1. A long-range protein-mediated radical transfer pathway appears to be responsible for the delivery of the radical from the tyrosine in R2 to the substrate on R1. The active site is located deep inside the protein in a very stable beta/alpha-barrel structure and a hydrogen bonded system leads from the surface to Cys439 at the active site which is in excellent position to remove a hydrogen from the 3' of the ribose of a bound substrate nucleotide.
核糖核苷酸还原酶含有一个对其活性至关重要的稳定有机自由基，该自由基位于酶的小亚基（称为R2）的一个酪氨酸残基上。然而，底物结合位点位于催化亚基（称为R1）中。一种由蛋白质介导的远程自由基转移途径似乎负责将自由基从R2中的酪氨酸传递到R1上的底物。活性位点位于蛋白质内部深处，呈非常稳定的β/α桶状结构，一个氢键系统从表面通向活性位点的半胱氨酸439，该位置非常有利于从结合的底物核苷酸核糖的3'位去除一个氢。
