The aim of this work was to study of the function of the 7.4 kb DNA in the central region of Tn5252. Through virulence assay, we would determine if this operon is involved in the pathogenesis of S. pneumoniae/. Furthermore, if this operon was involved in pathogenesis, we would carry out experiments to determine how this operon is involved in the pathogenesis of S. pneumoniae/. Findings and conclusions./ The streptococcal mobile element, Tn5252 (47 kb), carries an 8 kb operon containing four genes the largest of which is about 6 kb and highly homologous to eukaryotic SNF2-like DNA methyl transferase/helicases that are involved in gene regulation. The helicase operon was introduced into the chromosome of clinical pneumococcal strains by additive transformation. When introduced intraperitoneally into young female BALB/c mice, strains bearing the intact helicase operon were found to be significantly less pathogenic than the parental wild type strain or the one with the mutated operon. However, when introduced iDepartment of Biochemistry and Molecular Biolog
