Natural synthesis of a DNA-binding protein from the C-terminal domain of DNA gyrase A in Borrelia burgdorferi

We have identified a 34 kDa DNA-binding protein with an HU-like activity in the Lyme disease spirochete Borrelia burgdorferi. The 34 kDa protein is tr anslated from an abundant transcript initiated within the gene encoding the A subunit of DNA gyrase. Translation of the 34 kDa protein starts at resid ue 499 of GyrA and proceeds in the same reading frame as full-length GyrA, resulting in an N-terminal-truncated protein. The 34 kDa GyrA C-terminal do main, although not homologous, substitutes for HU in the formation of the T ype 1 complex in Mu transposition, and complements an HU-deficient strain o f Escherichia coli. This is the first example of constitutive expression of two gene products in the same open reading frame from a single gene in a p rokaryotic cellular system.