Expressió i funció de la ribonucleotidil reductasa codificada pels gens \i nrdEF\i0 en \i Salmonella typhimurium\i0 i altres bacteries

The genome of \i Salmonella typhimurium\i0 contains three operons which encode ribonucleotide reductase enzymes; the \i nrdDG\i0 operon codes for an anaerobic enzyme (class III) and the \i nrdAB\i0 and \i nrdHIEF\i0 operons both encode aerobic reductases (classes Ia and Ib, respectively). During aerobic growth, the AB-reductase is responsible for deoxyribonucleotide suynthesis, while the EF-reductase is not essential and is not expressed enough to support growth of AB\super -\nosuper mutants. The main goals of this project are a search for mechanisms that regulate expression of the \i nrdHIEF\i0 operon, as well as an investigation of the function of the EF reductase. A search for hypothetical proteins that may interact with the promoter region of the operon will be carried out. The interactions among the proteins of the EF enzymatic complex will be likewise investigated, with emphasis on the function of the \i nrdl\i0 gene product. Finally, we will analyze, both at the genetic and enzymatic levels, the function of the EF-reductase in bacterial species in which this enzyme is responsible for deoxyribonucleotide synthesis and is thus required for cell survival.