The effect of temperature on the synthesis and assembly of proticine 3 particles by Proteus mirabilis.

Proteus mirabilis CW977 produced high yields of the bacteriocin proticine 3 upon mitomycin C induction of cultures growing at 30 degrees C. The proticine was purified and found to have a relative density of 1.299 and to be composed of 10 proteins assembled into structures resembling contractile phage tails. When induction was performed at 41 degrees C neither proticine particles nor proticine activity was detected, although the growth rate of cells and degree of lysis were indistinguishable from that at 30 degrees C. Failure in proticine production was due to a 41 degrees C sensitive stage occurring between 60 and 90 min after the addition of mitomycin C. During this period at 30 degrees C, two proteins of mol. wt 58 000 and 41 000 were formed. These proteins were associated with events leading to the formation of proticine particles with biological activity. When the production of both proteins was prevented either by chloramphenicol or as a result of mutation or through sampling before they were formed, no proticine particles were found nor proticine activity detected. The synthesis of both proteins was also inhibited at 41 degrees C. Co-electrophoresis of the labelled proteins with unlabelled purified proticine confirmed that the protein of mol. wt 58 000 was a proticine structural protein. The protein of mol. wt 41 000 was not a structural component of proticine and its role, if any, in proticine 3 production is possibly that of an assembly protein.