STRUCTURE-FUNCTION STUDIES ON ESCHERICHIA-COLI METR PROTEIN, A PUTATIVE PROKARYOTIC LEUCINE ZIPPER PROTEIN

The Escherichia coli metR gene has been sequenced. The sequence predicts a protein of 317 amino acids and a calculated molecular weight of 35,628. This is about 15% larger than the protein from Salmonella typhimurium reported previously [Plamann, L. S. and Stauffer, G. V. (1987) J. Bacteriol. 169, 3932-3937]. The protein is a homodimer and contains a leucine zipper motif characteristic of many eukaryotic DNA-binding proteins. Replacement of two of the leucines in the leucine zipper region of the MetR protein, or substitution of proline for one of the leucines, results in loss of biological activity of the protein. In addition, truncation studies have identified a region on MetR that may be involved in the homocysteine activation of metE expression.