Identification and sequence determination of the host factor gene for bacteriophage Q beta.

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