THE MYCOBACTERIUM-TUBERCULOSIS PURINE BIOSYNTHETIC-PATHWAY - ISOLATION AND CHARACTERIZATION OF THE PURC AND PURL GENES

Genes from the Mycobacterium tuberculosis purine biosynthetic pathway were identified using purine auxotrophic mutants of Mycobacterium smeg matis obtained by Tn611 transposon mutagenesis. Two approaches were fo llowed in parallel. The first consisted of the complementation of the M. smegmatis purine auxotrophs using a M. tuberculosis H37Rv shuttle c osmid library. In the second approach, specific probes corresponding t o the regions adjacent to the insertion sites of Tn611 in the M. smegm atis genome were used to screen a M. tuberculosis plasmid library by c olony hybridization for inserts carrying homologous DNA fragments. Nuc leotide sequence analysis of two M. tuberculosis genes isolated by the se methods revealed high similarities with purC and purL genes from ot her bacterial and fungal sources, Transcriptional start sites were map ped for both genes, which revealed similar -10 boxes but with a higher GC content than the Escherichia coli sigma(70) consensus.