期刊
JOURNAL OF BACTERIOLOGY
卷 194, 期 11, 页码 2802-2808出版社
AMER SOC MICROBIOLOGY
DOI: 10.1128/JB.00061-12
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资金
- DOE [DE-SC0006871]
- U.S. Department of Energy (DOE) [DE-SC0006871] Funding Source: U.S. Department of Energy (DOE)
The ethylmalonyl coenzyme A (ethylmalonyl-CoA) pathway is one of the central methylotrophy pathways in Methylobacterium extorquens involved in glyoxylate generation and acetyl-CoA assimilation. Previous studies have elucidated the operation of the ethylmalonyl-CoA pathway in C-1 and C-2 assimilation, but the regulatory mechanisms for the ethylmalonyl-CoA pathway have not been reported. In this study, a TetR-type activator, CcrR, was shown to regulate the expression of crotonyl-CoA reductase/carboxylase, an enzyme of the ethylmalonyl-CoA pathway involved in the assimilation of C-1 and C-2 compounds in Methylobacterium extorquens AM1. A ccrR null mutant strain was impaired in its ability to grow on C-1 and C-2 compounds, correlating with the reduced activity of crotonyl-CoA reductase/carboxylase. Promoter fusion assays demonstrated that the activity of the promoter required for ccr expression (the katA-ccr promoter) decreased as much as 50% in the absence of ccrR compared to wildtype M. extorquens AM1. Gel mobility shift assays confirmed that CcrR directly binds to the region upstream of the katA-ccr promoter. A palindromic sequence upstream of katA at positions -334 to -321 with respect to the predicted translational start site was identified, and mutations in this region eliminated the gel retardation of the katA-ccr promoter region by CcrR. CcrR does not appear to regulate the expression of other-ethylmalonyl-CoA pathway genes, suggesting the existence of additional regulators.
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