Regulation of the Escherichia coli hfq gene encoding the host factor for phage Q beta.

The host factor (HF-I) for phage Q beta RNA replication is a small protein of 102 amino acid residues encoded by the hfq gene at 94.8 min on the Escherichia coli chromosome. The synthesis rate of HF-I at the exponential-growth phase is higher than at the stationary phase, and it increases concomitantly with the increase in cell growth rate. The intracellular level of HF-I is about 30,000 to 60,000 molecules per cell, the majority being associated with ribosomes as one of the salt wash proteins. Taken together, we suggest that HF-I is one of the growth-related proteins.