DNA-BINDING PROPERTIES OF THE HFQ GENE-PRODUCT OF ESCHERICHIA-COLI

We found that plasmids isolated by alkaline-lysis method occasionally showed abnormal mobility on agarose gel electrophoresis. This abnormal ity was not detected after phenol extraction of plasmids, indicating t hat it was caused by proteinous factor(s). A 15-kDa protein was found in the plasmid preparations on SDS-PAGE. The sequence of eighteen N-te rminal amino acid residues of the 15-kDa protein was identical with th e host factor I (HF-I) encoded by the hfq gene at 95 min on the Escher ichia coli chromosome map, which is known to be required for bacteriop hage Qa replication. The HF-I protein was purified and in vitro DNA bi nding experiment was carried out. HF-I bound to both supercoiled DNA a nd linear DNA and the binding of HF-I seemed to be sequence-nonspecifi c. (C) 1997 Academic Press.