A new methionine locus, metR, that encodes a trans-acting protein required for activation of metE and metH in Escherichia coli and Salmonella typhimurium
Open Access
- 1 April 1987
- journal article
- research article
- Published by American Society for Microbiology in Journal of Bacteriology
- Vol. 169 (4), 1391-1397
- https://doi.org/10.1128/jb.169.4.1391-1397.1987
Abstract
We isolated an Escherichia coli methionine auxotroph that displays a growth phenotype similar to that of known metF mutants but has elevated levels of 5,10-methylenetetrahydrofolate reductase, the metF gene product. Transduction analysis indicates that the mutant carries normal metE, metH, and metF genes; the phenotype is due to a single mutation, eliminating the possibility that the strain is a metE metH double mutant; and the new mutation is linked to the metE gene by P1 transduction. Plasmids carrying the Salmonella typhimurium metE gene and flanking regions complement the mutation, even when the plasmid-borne metE gene is inactivated. Enzyme assays show that the mutation results in a dramatic decrease in metE gene expression, a moderate decrease in metH gene expression, and a disruption of the metH-mediated vitamin B12 repression of the metE and metF genes. Our evidence suggests that the methionine auxotrophy caused by the new mutation is a result of insufficient production of both the vitamin B12-independent (metE) and vitamin B12-dependent (metH) transmethylase enzymes that are necessary for the synthesis of methionine from homocysteine. We propose that this mutation defines a positive regulatory gene, designated metR, whose product acts in trans to activate the metE and metH genes.This publication has 24 references indexed in Scilit:
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