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Structure-function studies on Escherichia coli MetR protein, a putative prokaryotic leucine zipper protein
M E Maxon1, J Wigboldus, N Brot
1Roche Research Center, Roche Institute of Molecular Biology, Nutley, NJ 07110-1199.
Abstract:
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. & 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.
Insights
The Escherichia coli MetR protein, a homodimer with a leucine zipper, is crucial for regulating gene expression. Mutations in its DNA-binding region abolish biological activity, highlighting its importance in homocysteine activation.
Area of Science:
- Molecular Biology
- Microbial Genetics
- Protein Structure
Background:
- The metR gene in Escherichia coli encodes a regulatory protein involved in methionine biosynthesis.
- Understanding the structure and function of MetR is essential for deciphering gene regulation pathways.
Purpose of the Study:
- To sequence the Escherichia coli metR gene and characterize the encoded MetR protein.
- To investigate the structural features of MetR, including its DNA-binding domain and potential role in gene activation.
Main Methods:
- Gene sequencing of Escherichia coli metR.
- Protein analysis, including molecular weight determination and identification of structural motifs.
- Mutagenesis studies to assess the impact of alterations in the leucine zipper region on protein activity.
- Truncation studies to map functional domains.
Main Results:
- The Escherichia coli metR gene sequence predicts a 317-amino acid protein (35,628 Da), larger than its Salmonella typhimurium counterpart.
- MetR functions as a homodimer and possesses a leucine zipper motif, common in eukaryotic DNA-binding proteins.
- Mutations within the leucine zipper region, specifically altering leucine residues or introducing proline, abolish MetR's biological activity.
- Truncation analyses suggest a specific region of MetR is involved in homocysteine activation of metE expression.
Conclusions:
- The MetR protein's leucine zipper motif is critical for its DNA-binding and regulatory functions.
- Specific regions of MetR are essential for mediating homocysteine activation of metE expression, providing insights into methionine metabolism regulation.