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- Title
Properties of the Corynebacterium glutamicum metC Gene Encoding Cystathionine Β-lyase.
- Authors
Jun-Won Kim; Hyung-Joon Kim; Younhee Kim; Myeong-Sok Lee; Heung-Shick Lee
- Abstract
The metC gene encoding the cystathionine β-lyase, the third enzyme in the methionine biosynthetic pathway, was isolated from Corynebacterium glutamicum by heterologous complementation of the Escherichia coli metC mutant. A DNA-sequence analysis of the cloned DNA identified two open-reading frames (ORFs) of ORF1 and ORF2 that consisted of 1,107 and 978 bp, respectively. A SDS-PAGE analysis identified a putative cystathionine β-lyase band with approximate Mr of 41,000 that consisted of 368 amino acids encoded from ORF1. The translational product of the gene showed no significant homology with that of the metC gene from other organisms. Introduction of the plasmid containing the metC gene into C. glutamicum resulted in a S-fold increase in the activity of the cystathionine β-lyase. The putative protein product of ORF2, encoding a protein product of 35,574 Da, consisted of 325 amino acids and was identical to the previously reported aecD gene product, except for the existence of two different amino acids. Like the aecD gene, when present in multiple copies, the metC gene conferred resistance to S-(β-aminoethyl)- cysteine, which is a toxic lysine analog. However, genetic and biochemical evidence suggests that the natural activity of the metC gene product is to mediate methionine biosynthesis in C. glutamicum. Mutant strains of metC were constructed, and the strains showed methionine prototrophy. The mutant strains completely lost their ability to show resistance to the S-(β-aminoethyl)-cysteine. These results suggest that, in addition to the transsulfuration, other biosynthetic pathway(s), such as a direct sulfhydrylation pathway, may be functional in C glutamicum as a parallel biosynthetic route for methionine.
- Subjects
CORYNEBACTERIUM; METHIONINE; AMINO acids; ESCHERICHIA; DNA; GENES; NUCLEIC acids; COMPLEMENTATION (Genetics); ENTEROBACTERIACEAE
- Publication
Molecules & Cells (Springer Nature), 2001, Vol 11, Issue 2, p220
- ISSN
1016-8478
- Publication type
Article
- DOI
10.1016/s1016-8478(23)17028-2