Tesis doctoral de Ignasi Roca SubirÁ
Ribonucleotide reductases (rnrs) are a group of enzymes that catalyze the reduction of ribonucleotides (ntps) to deoxyribonucleotides (dntps), thus providing all organisms with optimal amounts of the necessary buildings blocks for dna replication and repair. Three classes of rnrs have been characterized up to date according to their different mechanisms for radical generation, structural differences, allosteric regulation and oxygen dependence, all of them having in common the reaction mechanism and the use of an organic free radical to initiate catalysis. the genome of streptococcus pyogenes (group a streptococcus [gas]), a human pathogen responsible for many diverse infections, harbours the genes to synthesize two complete class ib rnrs (nrdhef/nrdi2 and nrdfie* respectively), while most streptococci only bear the nrdhef/nrdi2 genes. This work attempts to determine whether the presence of a second class ib rnr in s. Pyogenes accounts for a biological need or if it is simply the result of a vestigial burden. S. Pyogenes is the first prokaryotic organism where two distinct and complete ribonucleotide reductases of the same class are studied. linkage rt-pcr showed that both clusters are simultaneously transcribed and constitute two independent polycistronic units. The and subunits for these two systems were purified and biochemically characterized. The first system (nrdhef) proved active and presented an epr signal that matched that of other class ib tyrosyl radicals. Activity was dependent on the addition of magnesium and dtt and required ndps but not ntps as a substrate. It was also stimulated by datp as an allosteric effector but not by atp, as expected in a class ib enzyme. However, neither activity nor tyrosyl radical signal were ever detected from the nrdfie* cluster. When aligned together with other class ib enzymes, three out of the six iron binding residues within the subunit of the nrdfie* cluster were found not to be conserved. The iron contents of
Datos académicos de la tesis doctoral «Towards an understanding of ribonucleotide reduction in bacteria: a comprehensive study in streptococcus pyogenes and escherichia coli«
- Título de la tesis: Towards an understanding of ribonucleotide reduction in bacteria: a comprehensive study in streptococcus pyogenes and escherichia coli
- Autor: Ignasi Roca SubirÁ
- Universidad: Autónoma de barcelona
- Fecha de lectura de la tesis: 18/06/2007
Dirección y tribunal
- Director de la tesis
- Isidre Gibert González
- Tribunal
- Presidente del tribunal: josep Casadesus pursals
- albert Jordan vallés (vocal)
- De la torre Mª ángeles (vocal)
- alex Kasrayan (vocal)