Intracellular location of catabolite activator protein of Escherichia coli.

The catabolite activator protein was assayed in extracts from the minicell-producing Escherichia coli strain P678-54. The level of catabolite activator protein was found to be the same in both parent cells and purified minicells, regardless of whether the bacteria were grown on glucose (which leads to low intracellular cyclic adenosine monophosphate levels) or on glycerol-yeast extract or LB broth (which lead to high cyclic adenosine monophosphate concentrations in the cell). Thus, at any given time most catabolite activator protein molecules are found in the cytoplasm. The implications of this for the mechanism of catabolite activator protein action at catabolite-sensitive operons are discussed.