A new hybrid promoter and its expression vector in Escherichia coli.

A new hybrid promoter, "pac", comprising the '-35' region of the bacteriophage T5 P25 gene promoter and the '-10' and the operator regions of the lacUV5 promoter, was chemically synthesized and used to construct a new expression vector. The activity of the hybrid promoter was compared with that of the tac (trp: lac fusion) promoter, which is widely used as a strong and controllable promoter. The activity of the pac promoter was found to be stronger by about 3-fold than that of tac when assayed with the chloramphenicol acetyltransferase (CAT) system. The pac promoter, however, was not repressed as efficiently as the tac promoter