CELL-GROWTH AND LAMBDA-PHAGE DEVELOPMENT CONTROLLED BY THE SAME ESSENTIAL ESCHERICHIA-COLI GENE, FTSH HFLB

The lambda phage choice between lysis and lysogeny is influenced by ce rtain host functions in Escherichia coli. We found that the frequency of lambda lysogenization is markedly increased in the ftsH1 temperatur e-sensitive mutant. The ftsH gene, previously shown to code for an ess ential inner membrane protein with putative ATPase activity, is identi cal to hflB, a gene involved in the stability of the phage cII activat or protein. The lysogenic decision controlled by FtsH/HflB is independ ent of that controlled by the protease HflA. Overproduction of FtsH/Hf lB suppresses the high frequency of lysogenization in an hfl4 null mut ant. The FtsH/HflB protein, which stimulates cII degradation, may be a component of an HflA-independent proteolytic pathway, or it may act a s a chaperone, maintaining cII in a conformation subject to proteolysi s via such a pathway. Suppressor mutations of ftsH1 temperature-sensit ive lethality, located in the fur gene (coding for the ferric uptake r egulator), did not restore FtsH/HflB activity with respect to lambda l ysogenization.