Structural analysis of the mde operon involved in L-methionine degrative metabolism of Pseudomonas putida
1998
Inoue, H. (Okayama Univ. (Japan). Faculty of Agriculture) | Tamura, T. | Inagaki, K. | Tanaka, H.
The mde operon and an upstream regulatory gene (mdeR) have been cloned and sequenced from Pseudomonas putida chromosomal DNA. The mde operon contains two structural genes involved in L-methionine degradative metabolism, which are mdeA (L-methionine gamma-lyase gene) and mdeB (a gene encoding a homologous protein to the E1) component of pyruvate dehydrogenase complex). A rho-independent terminator was present just downstream of mdeB and open reading frames corresponding to other components of alpha-keto acid dehydrogenase complex were not found. When the mdeB gene product was overproduced in Escherichia coli, the E1 activity of the cell extract showed high specificity for alpha-ketobutyrate rather than pyruvate. These results suggest that mde B encodes a novel E1 component, alpha-ketobutyrate dehydrogenase E1 component, and plays an important role in the metabolism of alpha-ketobutyrate produced by L-methionine gamma-lyase from L-methionine. In addition, we found that mdeR gene was located on the opposite strand and began at 127 bp from the translational start site of mdeA. The mdeR gene product has been identified as a member of the leucine responsive regulatory protein (Lrp) family and revealed to act as an essential positive regulator allowing the expression of the mdeAB operon
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