The AmiC protein in Pseudomonas aeruginosa is the negative regulator and ligand receptor for an amide-inducible aliphatic amidase operon. In the wild-type PAC1 strain, amidase expression is induced by acetamide or lactamide, but not by butyramide. A mutant strain of P ...
The AmiC protein in Pseudomonas aeruginosa is the negative regulator and ligand receptor for an amide-inducible aliphatic amidase operon. In the wild-type PAC1 strain, amidase expression is induced by acetamide or lactamide, but not by butyramide. A mutant strain of P. aeruginosa, PAC181, was selected for its sensitivity to induction by butyramide. The molecular basis for the butyramide inducible phenotype of P.aeruginosa PAC181 has now been determined, and results from a Thr-->Asn mutation at position 106 in PAC181-AmiC. In the wild-type PAC1-AmiC protein this residue forms part of the side wall of the amide-binding pocket but does not interact with the acetamide ligand directly. In the crystal structure of PAC181-AmiC complexed with butyramide, the Thr-->Asn mutation increases the size of the ligand binding site such that the mutant protein is able to close into its 'on' configuration even in the presence of butyramide. Although the mutation allows butyramide to be recognized as an inducer of amidase expression, the mutation is structurally sub-optimal, and produces a significant decrease in the stability of the mutant protein.
Related Citations:
Crystal Structure of Amic: The Controller of Transcription Antitermination in the Amidase Operon of Pseudomonas Aeruginosa Pearl, L.H., O'Hara, B.P., Drew, R.E., Wilson, S.A. (1994) EMBO J 13: 5810
Antitermination of Amidase Expression in Pseudomonas Aeruginosa is Controlled by a Novel Cytoplasmic Amide- Binding Protein Wilson, S.A., Wachira, S.J., Drew, R.E., Jones, D., Pearl, L.H. (1993) EMBO J 12: 3637
Crystallization and Preliminary X-Ray Data for the Negative Regulator (Amic) of the Amidase Operon of Pseudomonas Aeruginosa Wilson, S.A., Chayen, N.E., Hemmings, A.M., Drew, R.E., Pearl, L.H. (1991) J Mol Biol 222: 869
Organizational Affiliation:
Department of Biochemistry and Molecular Biology and Joint UCL/LICR X-Ray Crystallography Laboratory, University College London, Gower Street, London WC1E 6BT, UK.
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