Purification and characterisation of a small DNA-binding protein, HB, from Bacillus globigii

We have purified a small, heat-stable DNA-binding protein from Bacillus globigii: HB protein. The protein binds cooperatively to double-stranded DNA and the DNA-protein complexes are destabilised by the presence of moderate (0.1 M) levels of monovalent cations or by low levels (10 mM) of Mg2+. We have also purified two small DNA-binding proteins from Escherichia coli, NS1 and NS2 [Suryanarayana, T. and Subramanian, A.R. (1978) Biochim. Biophys. Acta, 520, 342-357], also known as HU protein [Rouvière-Yaniv, J. and Gros, F. (1975) Proc. Natl Acad. Sci. USA, 72, 3428-3432] that have been extensively studied by others. We have prepared antibodies against all three proteins and have shown that all three are, by immunological criteria, related.