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Published June 15, 1993 | public
Journal Article Open

Genetics of serine pathway enzymes in Methylobacterium extorquens AM1: phosphoenolpyruvate carboxylase and malyl coenzyme A lyase


Methylobacterium extorquens AM1 is a facultative methylotrophic bacterium that uses the serine pathway for formaldehyde incorporation as its assimilation pathway during growth on one-carbon compounds. A DNA region from M. extorquens AM1 previously shown to contain genes for the serine pathway enzymes malyl coenzyme A (CoA) lyase and hydroxypyruvate reductase has been characterized in more detail. Insertion mutagenesis revealed an additional region required for growth on one-carbon compounds, and all of the insertion mutants in this region lacked activity for another serine pathway enzyme, the acetyl- CoA-independent phosphoenolpyruvate (PEP) carboxylase. Expression analysis with Escherichia coli of DNA fragments that included the malyl- CoA lyase and PEP carboxylase regions identified five polypeptides, all transcribed in the same direction. Three of these polypeptides were expressed from the region necessary for the acetyl-CoA-independent PEP carboxylase, one was expressed from the region containing the malyl-CoA lyase gene, and the fifth was expressed from a region immediately downstream from the gene encoding hydroxypyruvate reductase. All six genes are transcribed in the same direction, but the transposon insertion data suggest that they are not all cotranscribed.

Additional Information

Copyright © 1993, American Society for Microbiology Received 28 December 1992/Accepted 9 April 1993 This work was supported by a grant from the Department of Energy (no. DEFOGO-87ER13753). We thank Stan Tabor for supplying plasmids pGP1-2, pT7-3, pT7-5, and pT7-6.


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