DNA-binding proteins possibly involved in regulation of the post-logarithmic-phase expression of lipoprotein p35 in Borrelia burgdorferi

previously, we have shown that the transcription of p35, a lipoprotein gene of Borrelia burgdorferi, is upregulated or initiated during the post-logar ithmic bacterial growth phase in vitro. To identify potential regulatory fa ctors, we examined the formation of DNA-protein complexes by electromobilit y shift assay, using a 157-bp DNA fragment that spans the p35 promoter regi on and cell-free extracts of spirochetes harvested from both logarithmic an d stationary growth phases. The binding properties of the extracts with the promoter region of the flaB gene, a constitutively expressed, growth-phase -independent gene, were also compared. The results from these experiments d emonstrate that B. burgdorferi stationary-phase cell-free extracts have a g rowth-phase-dependent DNA binding protein that interacts specifically with the p35 promoter region. We show, in addition, that a segment from the 157- bp p35 promoter region which contains both a T-rich stretch and an inverted repeat is able to compete off the stationary-phase-specific complex when t he segment is present in molar excess.