Purification and characterization of the 17 K protein, a DNA-binding protein from Escherichia coli

A basic protein of molecular mass 17 kDa (protein 17 K) which binds to relaxed DNA has been isolated and purified to homogeneity from Escherichia coli cells. The protein behaves as a tetramer in solution and there are 4800 monomers per cell in exponentially growing cells. The amino-acid composition and N-terminal sequence were determined. No effect of the protein on in vitro transcription was observed. The protein was shown to be different from the Ssb protein (Sigal, N. et al. (1972) Proc. Natl. Acad. Sci. USA 69, 3537-3541), protein H1 (Cukier-Kahn et al. (1972) Proc. Natl. Acad. Sci. USA 69, 3643-3647) and the HLP-1 protein (Lathe, R. et al. (1980) Proc. Natl. Acad. Sci. USA 77, 3548-3552).