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The E. coli NusA carboxy-terminal domains are structurally similar and show specific RNAP- and lambdaN interaction.

ABSTRACT: The carboxy-terminal domain of the transcription factor Escherichia coli NusA, NusACTD, interacts with the protein N of bacteriophage lambda, lambdaN, and the carboxyl terminus of the E. coli RNA polymerase alpha subunit, alphaCTD. We solved the solution structure of the unbound NusACTD with high-resolution nuclear magnetic resonance (NMR). Additionally, we investigated the binding sites of lambdaN and alphaCTD on NusACTD using NMR titrations. The solution structure of NusACTD shows two structurally similar subdomains, NusA(353-416) and NusA(431-490), matching approximately two homologous acidic sequence repeats. Further characterization of NusACTD with 15N NMR relaxation data suggests that the interdomain region is only weakly structured and that the subdomains are not interacting. Both subdomains adopt an (HhH)2 fold. These folds are normally involved in DNA-protein and protein-protein interactions. NMR titration experiments show clear differences of the interactions of these two domains with alphaCTD and lambdaN, in spite of their structural similarity.

SUBMITTER: Eisenmann A

PROVIDER: S-EPMC2279313 | biostudies-literature | 2005 Aug

REPOSITORIES: biostudies-literature

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The E. coli NusA carboxy-terminal domains are structurally similar and show specific RNAP- and lambdaN interaction.

Eisenmann Anke A Schwarz Sabine S Prasch Stefan S Schweimer Kristian K Rösch Paul P

Protein science : a publication of the Protein Society 20050629 8

The carboxy-terminal domain of the transcription factor Escherichia coli NusA, NusACTD, interacts with the protein N of bacteriophage lambda, lambdaN, and the carboxyl terminus of the E. coli RNA polymerase alpha subunit, alphaCTD. We solved the solution structure of the unbound NusACTD with high-resolution nuclear magnetic resonance (NMR). Additionally, we investigated the binding sites of lambdaN and alphaCTD on NusACTD using NMR titrations. The solution structure of NusACTD shows two structur ...[more]

PMID: 15987884

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Project description:Bacillus subtilis Spx is a global transcriptional regulator that is conserved among Gram-positive bacteria, in which Spx is required for preventing oxidatively induced proteotoxicity. Upon stress induction, Spx engages RNA polymerase (RNAP) through interaction with the C-terminal domain of the rpoA-encoded RNAP ? subunit (?CTD). Previous mutational analysis of rpoA revealed that substitutions of Y263 in ?CTD severely impaired Spx-activated transcription. Attempts to substitute alanine for ?CTD R261, R268, R289, E255, E298, and K294 were unsuccessful, suggesting that these residues are essential. To determine whether these RpoA residues were required for productive Spx-RNAP interaction, we ectopically expressed the putatively lethal rpoA mutant alleles in the rpoAY263C mutant, where "Y263C" indicates the amino acid change that results from mutation of the allele. By complementation analysis, we show that Spx-bound ?CTD amino acid residues are not essential for Spx-activated transcription in vivo but that R261A, E298A, and E255A mutants confer a partial defect in NaCl-stress induction of Spx-controlled genes. In addition, strains expressing rpoAE255A are defective in disulfide stress resistance and produce RNAP having a reduced affinity for Spx. The E255 residue corresponds to Escherichia coli ?D259, which has been implicated in ?CTD-?70 interaction (?70 R603, corresponding to R362 of B. subtilis ?A). However, the combined rpoAE255A and sigAR362A mutations have an additive negative effect on Spx-dependent expression, suggesting the residues' differing roles in Spx-activated transcription. Our findings suggest that, while ?CTD is essential for Spx-activated transcription, Spx is the primary DNA-binding determinant of the Spx-?CTD complex.IMPORTANCE Though extensively studied in Escherichia coli, the role of ?CTD in activator-stimulated transcription is largely uncharacterized in Bacillus subtilis Here, we conduct phenotypic analyses of putatively lethal ?CTD alanine codon substitution mutants to determine whether these residues function in specific DNA binding at the Spx-?CTD-DNA interface. Our findings suggest that multisubunit RNAP contact to Spx is optimal for activation while Spx fulfills the most stringent requirement of upstream promoter binding. Furthermore, several ?CTD residues targeted for mutagenesis in this study are conserved among many bacterial species and thus insights on their function in other regulatory systems may be suggested herein.

Dataset Information

The E. coli NusA carboxy-terminal domains are structurally similar and show specific RNAP- and lambdaN interaction.

Publications

The E. coli NusA carboxy-terminal domains are structurally similar and show specific RNAP- and lambdaN interaction.

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