[Isolation and properties of B. subtilis DNA-binding proteins inhibiting ATP-dependent deoxyribonuclease]

The fraction inhibiting ATP-dependent DNAase and some other enzyme activities was found in B. subtilis cell extracts. Two methods of its isolation were elaborated. It is established that the inhibiting activity fraction represents a set of some positively charged thermostable proteins of low molecular weight (M 9000--25 000). The inhibiting effect of the proteins in question may be attributed to their ability to form a complex with DNA. The complex is formed in low ionic strength conditions. The elevation of NaCl concentration to 0,3 M removes some proteins from the complex and causes the complete loss of inhibiting activity. At 0,5 M NaCl DNA-protein complex is completely dissociated. The discovered proteins seems to be localized in DNA-membrane cell fraction. It is supposed that these proteins (or some of them) are the structural ones of the bacterial nucleoid.