ANTITERMINATION OF AMIDASE EXPRESSION IN PSEUDOMONAS-AERUGINOSA IS CONTROLLED BY A NOVEL CYTOPLASMIC AMIDE-BINDING PROTEIN

Amide-inducible expression of the aliphatic amidase system of Pseudomo nas aeruginosa can be reconstituted in Escherichia coli with only the amidase structural gene amiE, the negative regulator amiC and the posi tive regulator amiR, a transcription antitermination factor. Complemen tation experiments in E.coli suggest that negative control of amidase expression by AmiC is mediated by a protein - protein interaction with AmiR. Purified AmiC binds acetamide with a K(D) of 3.7 muM in equilib rium dialysis studies, and therefore AmiC appears to be the sensory pa rtner of the AmiC/AmiR pair of regulatory proteins, responding to the presence of amides. Sequence analysis techniques suggest that AmiC is a member of the structural family of periplasmic binding proteins, but has a distinct and novel cytoplasmic role.