Ribonucleotide reductase conformers

Labarre JF (1978) Conformational Analysis in Inorganic Chemistry Semi-Empirical Quantum Calculation vs. Experiment. 35 1-35 Lammers M, Follmann H (1983) The Ribonucleotide Reductases A Unique Group of Metalloenzymes Essential for Cell Proliferation. 54 27-91 Le Brun NE, Thomson AJ, Moore GR (1997) Metal Centres of Bacterioferritins of Non-Heam-Iron-Containing Cyrochromes 6557. 88 103-138... 

Unfortunately, despite the great stability of the tyrosine radical of ribonucleotide reductase [69], the crystals available for diffraction contain the enzyme in its non-radical form [107]. However, the tyrosine residue (Tyr-122) known to convert to the radical is buried in the protein [99] and the position and structure of the tyrosine residue in the crystal is consistent with spectroscopic data for the radical form as with cytochrome c peroxidase, it appears unlikely that major conformational changes occur subsequent to radical formation. 

The distance dependence of the individual hopping steps is smaller in DNA than in peptides because DNA is more efficient than the peptides as a mediator of the charge transport. On the other hand, peptides are more flexible than DNA double strands and the distances between side-chains of amino acids in peptides can be reduced by conformational changes. The influence of peptide sequence and tertiary structure still remains to be investigated in detail. Investigations of ribonucleotide reductase, DNA photolyase and photosystem II point to the importance of aromatic amino acids such as tyrosine and tryptophan for ET in these proteins. 

In view of these consistent correlations of primary stznicture, conformation, and enzyme activity In nucleotides It was surprising to find that 8-bromo-dATP acts as a good activator of ribonucleotide reductase like other deoxyrlbo-nucleotldes [28]. One explanation would be that the deoxy-... 

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