MECHANISM OF SYNTHESIS OF SECRETORY PROTEIN AND ITS GENE EXPRESSION IN ESCHERICHIA CORI

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Mechanism of the expression of the genes coding for major outer membrane protein, OmpC and OmpF, has been studied. Many important results and implications about the morecular mechanism of the regulation have been obtained. Deletion as well as base substitution analysis of the ompC and ompF genes revealed that 60 to 70 base pair sequences extending upstream from the respective canonical promoters (-35,-10 regions) are required for the ompC and ompF promoters to function fully, and that OmpR protein activates the expression of these genes most likely by binding to the upstream regions of the ompC and ompF promoters. Several mutant ompR genes as well as the wild-type ompR gene have been cloned, and the nucleotide sequences have been determined. The fact that the osmoregulatory profiles differed depending on the site of mutation on the ompR gene strongly supported the view that OmpR protein is directly involved in osmoregulation, and that this protein takes a multimeric structure as a functional unit. Isolation of an envZ deletion mutant revealed that EnvZ protein appeared to play an important role not only in the full expression of the ompC and ompF genes, but also in the fluctuation of the expression depending on the medium osmolarity. OmpR protein was purified to homogeneity and characterized. Furthermore, direct binding of OmpR protein to the promoter regions of the ompC and ompF genes was demonstrated.