7R1R

RIBONUCLEOTIDE REDUCTASE E441Q MUTANT R1 PROTEIN FROM ESCHERICHIA COLI

Summary for 7R1R

• Entry DOI: 10.2210/pdb7r1r/pdb
• Descriptor: RIBONUCLEOTIDE REDUCTASE R1 PROTEIN, RIBONUCLEOTIDE REDUCTASE R2 PROTEIN (3 entities in total)
• Functional Keywords: ribonucleotide reductase, deoxyribonucleotide synthesis, radical chemistry, allosteric regulation, specificity, complex (oxidoreductase-peptide), complex (oxidoreductase-peptide) complex, complex (oxidoreductase/peptide)
• Biological source: Escherichia coli; More
• Total number of polymer chains: 7
• Total formula weight: 266713.87

Authors

Eriksson, M.,Eklund, H. (deposition date: 1997-09-17, release date: 1998-03-18, Last modification date: 2024-10-23)

Primary citation

Persson, A.L.,Eriksson, M.,Katterle, B.,Potsch, S.,Sahlin, M.,Sjoberg, B.M.
A new mechanism-based radical intermediate in a mutant R1 protein affecting the catalytically essential Glu441 in Escherichia coli ribonucleotide reductase.
J.Biol.Chem., 272:31533-31541, 1997

PubMed Abstract: The invariant active site residue Glu441 in protein R1 of ribonucleotide reductase from Escherichia coli has been engineered to alanine, aspartic acid, and glutamic acid. Each mutant protein was structurally and enzymatically characterized. Glu441 contributes to substrate binding, and a carboxylate side chain at position 441 is essential for catalysis. The most intriguing results are the suicidal mechanism-based reaction intermediates observed when R1 E441Q is incubated with protein R2 and natural substrates (CDP and GDP). In a consecutive reaction sequence, we observe at least three clearly discernible steps: (i) a rapid decay (k1 >/= 1.2 s-1) of the catalytically essential tyrosyl radical of protein R2 concomitant with formation of an early transient radical intermediate species, (ii) a slower decay (k2 = 0.03 s-1) of the early intermediate concomitant with formation of another intermediate with a triplet EPR signal, and (iii) decay (k3 = 0.004 s-1) of the latter concomitant with formation of a characteristic substrate degradation product. The characteristics of the triplet EPR signal are compatible with a substrate radical intermediate (most likely localized at the 3'-position of the ribose moiety of the substrate nucleotide) postulated to occur in the wild type reaction mechanism as well.

PubMed: 9395490
DOI: 10.1074/jbc.272.50.31533

Experimental method

X-RAY DIFFRACTION (3.1 Å)