Identification and sequence determination of the host factor gene for bacteriophage q_β

The host factor (HF-l) required for phage Q_β RNA-directed synthesis of complementary minus-strand RNA was purified to homogeneity from phage-infected Escherichia coil cells. The hfq gene encoding HF-l was cloned using synthetic probes designed based on the partial amino acid sequence of HF-l, and mapped at 94.8 mln on the E. coil chromosome downstream of the miaA gene involved in 2-methylthlo-N₆-(isopentyl) adenosine (ms²i⁶A) tRNA modification. Sequence determination of the cloned hfq gene Indicated that HF-l is a small protein of Mr 11, 166 consisting of 102 amino acid residues.