MOLECULAR ANALYSIS OF THE DNAK LOCUS OF LEPTOSPIRA-INTERROGANS SEROVAR COPENHAGENI

Analysis of the dnaK locus of Leptospira interrogans serovar Copenhage ni identified four genes in the order hrcA, grpE, dnaK and dnaJ. This is the first time a homologue of hrcA has been identified in a spiroch ete. The hrcA gene and a regulatory sequence, designated CIRCE, play a significant role in the regulation of the dnaK locus of several Gram organisms. Their presence upstream of dnaK in Leptospira suggested a similiar regulatory mechanism. Transcriptional analysis using reverse transcriptase-PCR demonstrated transcription of all four genes and ind icated that hrcA and grpE were co-transcribed, as were grpE and dnaK. Whilst hrcA, grpE and dnaK were closely linked on the chromosome, tran scription terminators between dnaK and dnaJ and downstream of dnaJ sug gested that this latter gene exists in its own operon. Primer extensio n analysis located functional promoters upstream of hrcA and grpE; how ever, no evidence of a functional promoter could be found for dnaJ. Mo reover, transcripts encompassing the first three genes or the entire l ocus could not be demonstrated, suggesting that the four genes are reg ulated independently at the transcriptional level. These results indic ate that the regulation of the dnaK locus of Leptospira differs somewh at from that observed in other organisms. (C) 1998 Elsevier Science B. V. All rights reserved.