Download MendeleySubstitution of manganese for iron in ribonucleotide reductase from Escherichia coli. Spectroscopic and crystallographic characterization.
Atta, M., Nordlund, P., Aberg, A., Eklund, H., Fontecave, M.(1992) J Biol Chem 267: 20682-20688
- PubMed: 1328209
- Primary Citation of Related Structures:
1MRR - PubMed Abstract:
Each polypeptide chain of protein R2, the small subunit of ribonucleotide reductase from Escherichia coli, contains a stable tyrosyl radical and two antiferromagnetically coupled oxo-bridged ferric ions. A refined structure of R2 has been recently obtained. R2 can be converted into apoR2 by chelating out the metal cofactor and scavenging the radical. This study shows that apoR2 has a very strong affinity for four stable Mn2+ ions. The manganese-containing form of R2, named Mn-R2, has been studied by EPR spectroscopy and x-ray crystallography. It contains two binuclear manganese clusters in which the two manganese ions occupy the natural iron-binding sites and are only bridged by carboxylates from glutamates 115 and 238. This in turn explains why the spin-exchange interaction between the two ions is very weak and why Mn-R2 is EPR active. Mn-R2 could provide a model for the native diferrous form of protein R2, and a detailed molecular mechanism for the reduction of the iron center of protein R2 is proposed.
Organizational Affiliation:
Laboratoire d'Etudes Dynamiques et Structurales de la Sélectivité, URA Centre National de la Recherche Scientifique 0332, Université J. Fourier, Grenoble, France.
