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B12-dependent ribonucleotide reductases from deeply rooted eubacteria are structurally related to the aerobic enzyme from Escherichia coli.
- Source :
-
Proceedings of the National Academy of Sciences of the United States of America [Proc Natl Acad Sci U S A] 1997 Dec 09; Vol. 94 (25), pp. 13487-92. - Publication Year :
- 1997
-
Abstract
- The ribonucleotide reductases from three ancient eubacteria, the hyperthermophilic Thermotoga maritima (TM), the radioresistant Deinococcus radiodurans (DR), and the thermophilic photosynthetic Chloroflexus aurantiacus, were found to be coenzyme-B12 (class II) enzymes, similar to the earlier described reductases from the archaebacteria Thermoplasma acidophila and Pyrococcus furiosus. Reduction of CDP by the purified TM and DR enzymes requires adenosylcobalamin and DTT. dATP is a positive allosteric effector, but stimulation of the TM enzyme only occurs close to the temperature optimum of 80-90 degrees C. The TM and DR genes were cloned by PCR from peptide sequence information. The TM gene was sequenced completely and expressed in Escherichia coli. The deduced amino acid sequences of the two eubacterial enzymes are homologous to those of the archaebacteria. They can also be aligned to the sequence of the large protein of the aerobic E. coli ribonucleotide reductase that belongs to a different class (class I), which is not dependent on B12. Structure determinations of the E. coli reductase complexed with substrate and allosteric effectors earlier demonstrated a 10-stranded beta/alpha-barrel in the active site. From the conservation of substrate- and effector-binding residues we propose that the B12-dependent class II enzymes contain a similar barrel.
- Subjects :
- Amino Acid Sequence
Bacteria genetics
Base Sequence
Binding Sites
Chromosome Mapping
Cloning, Molecular
Cytidine Diphosphate metabolism
Cytidine Triphosphate metabolism
DNA Primers genetics
Escherichia coli genetics
Genes, Bacterial
Gram-Negative Anaerobic Bacteria enzymology
Gram-Negative Anaerobic Bacteria genetics
Gram-Positive Cocci enzymology
Gram-Positive Cocci genetics
Molecular Sequence Data
Polymerase Chain Reaction
Ribonucleotide Reductases genetics
Sequence Homology, Amino Acid
Substrate Specificity
Temperature
Bacteria enzymology
Cobamides metabolism
Escherichia coli enzymology
Ribonucleotide Reductases chemistry
Ribonucleotide Reductases metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0027-8424
- Volume :
- 94
- Issue :
- 25
- Database :
- MEDLINE
- Journal :
- Proceedings of the National Academy of Sciences of the United States of America
- Publication Type :
- Academic Journal
- Accession number :
- 9391052
- Full Text :
- https://doi.org/10.1073/pnas.94.25.13487