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The AbrB2 autorepressor, expressed from an atypical promoter, represses the hydrogenase operon to regulate hydrogen production in Synechocystis strain PCC6803.

ABSTRACT: We have thoroughly investigated the abrB2 gene (sll0822) encoding an AbrB-like regulator in the wild-type strain of the model cyanobacterium Synechocystis strain PCC6803. We report that abrB2 is expressed from an active but atypical promoter that possesses an extended -10 element (TGTAATAT) that compensates for the absence of a -35 box. Strengthening the biological significance of these data, we found that the occurrence of an extended -10 promoter box and the absence of a -35 element are two well-conserved features in abrB2 genes from other cyanobacteria. We also show that AbrB2 is an autorepressor that is dispensable to cell growth under standard laboratory conditions. Furthermore, we demonstrate that AbrB2 also represses the hox operon, which encodes the Ni-Fe hydrogenase of biotechnological interest, and that the hox operon is weakly expressed even though it possesses the two sequences resembling canonical -10 and -35 promoter boxes. In both the AbrB2-repressed promoters of the abrB2 gene and the hox operon, we found a repeated DNA motif [TT-(N(5))-AAC], which could be involved in AbrB2 repression. Supporting this hypothesis, we found that a TT-to-GG mutation of one of these elements increased the activity of the abrB2 promoter. We think that our abrB2-deleted mutant with increased expression of the hox operon and hydrogenase activity, together with the reporter plasmids we constructed to analyze the abrB2 gene and the hox operon, will serve as useful tools to decipher the function and the regulation of hydrogen production in Synechocystis.

SUBMITTER: Dutheil J

PROVIDER: S-EPMC3457224 | biostudies-literature | 2012 Oct

REPOSITORIES: biostudies-literature

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The AbrB2 autorepressor, expressed from an atypical promoter, represses the hydrogenase operon to regulate hydrogen production in Synechocystis strain PCC6803.

Dutheil Jérémy J Saenkham Panatda P Sakr Samer S Leplat Christophe C Ortega-Ramos Marcia M Bottin Hervé H Cournac Laurent L Cassier-Chauvat Corinne C Chauvat Franck F

Journal of bacteriology 20120803 19

We have thoroughly investigated the abrB2 gene (sll0822) encoding an AbrB-like regulator in the wild-type strain of the model cyanobacterium Synechocystis strain PCC6803. We report that abrB2 is expressed from an active but atypical promoter that possesses an extended -10 element (TGTAATAT) that compensates for the absence of a -35 box. Strengthening the biological significance of these data, we found that the occurrence of an extended -10 promoter box and the absence of a -35 element are two we ...[more]

PMID: 22865847

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Project description:BACKGROUND: Molecular hydrogen is an environmentally-clean fuel and the reversible (bi-directional) hydrogenase of the cyanobacterium Synechocystis sp. PCC 6803 as well as the native Escherichia coli hydrogenase 3 hold great promise for hydrogen generation. These enzymes perform the simple reaction 2H+ + 2e- <--> H2 (g). RESULTS: Hydrogen yields were enhanced up to 41-fold by cloning the bidirectional hydrogenase (encoded by hoxEFUYH) from the cyanobacterium into E. coli. Using an optimized medium, E. coli cells expressing hoxEFUYH also produced twice as much hydrogen as the well-studied Enterobacter aerogenes HU-101, and hydrogen gas bubbles are clearly visible from the cultures. Overexpression of HoxU alone (small diaphorase subunit) accounts for 43% of the additional hydrogen produced by HoxEFUYH. In addition, hydrogen production in E. coli mutants with defects in the native formate hydrogenlyase system show that the cyanobacterial hydrogenase depends on both the native E. coli hydrogenase 3 as well as on its maturation proteins. Hydrogen absorption by cells expressing hoxEFUYH was up to 10 times lower than cells which lack the cloned cyanobacterial hydrogenase; hence, the enhanced hydrogen production in the presence of hoxEFUYH is due to inhibition of hydrogen uptake activity in E. coli. Hydrogen uptake by cells expressing hoxEFUYH was suppressed in three wild-type strains and in two hycE mutants but not in a double mutant defective in hydrogenase 1 and hydrogenase 2; hence, the active cyanobacterial locus suppresses hydrogen uptake by hydrogenase 1 and hydrogenase 2 but not by hydrogenase 3. Differential gene expression indicated that overexpression of HoxEFUYH does not alter expression of the native E. coli hydrogenase system; instead, biofilm-related genes are differentially regulated by expression of the cyanobacterial enzymes which resulted in 2-fold elevated biofilm formation. This appears to be the first enhanced hydrogen production by cloning a cyanobacterial enzyme into a heterologous host. CONCLUSION: Enhanced hydrogen production in E. coli cells expressing the cyanobacterial HoxEFUYH is by inhibiting hydrogen uptake of both hydrogenase 1 and hydrogenase 2.

Dataset Information

The AbrB2 autorepressor, expressed from an atypical promoter, represses the hydrogenase operon to regulate hydrogen production in Synechocystis strain PCC6803.

Publications

The AbrB2 autorepressor, expressed from an atypical promoter, represses the hydrogenase operon to regulate hydrogen production in Synechocystis strain PCC6803.

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