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Structure of the carboxy-terminal domain of Mycobacterium tuberculosis CarD protein: an essential rRNA transcriptional regulator.

ABSTRACT: The CarD protein is highly expressed in mycobacterial strains under basal conditions and is transcriptionally induced during multiple types of genotoxic stress and starvation. The CarD protein binds the ? subunit of RNA polymerase and influences gene expression. The disruption of interactions between CarD and the ? subunit of RNA polymerase has a significant effect on mycobacterial survival, resistance to stress and pathogenesis. To understand the structure of CarD and its interaction with the ? subunit of RNA polymerase, Mycobacterium tuberculosis CarD (MtbCarD) and the Thermus aquaticus RNA polymerase ? subunit were recombinantly expressed and purified. Secondary-structure analysis using circular-dichroism spectroscopy indicated that MtbCarD contains ? 60% ?-helix, ? 7% ?-sheet and ? 33% random-coil structure. The C-terminal domain of MtbCarD (CarD(83-161)) was crystallized and its X-ray structure was determined at 2.1 Å resolution. CarD(83-161) forms a distorted Y-shaped structure containing bundles of three helices connected by a loop. The residues forming the distorted Y-shaped structure are highly conserved in CarD sequences from other mycobacterial species. Comparison of the CarD(83-161) structure with the recently determined full-length M. tuberculosis and T. thermophilus CarD crystal structures revealed structural differences in residues 141-161 of the C-terminal domain of the CarD(83-161) structure. The structural changes in the CarD(83-161) structure occurred owing to proteolysis and crystallization artifacts.

SUBMITTER: Gangwar SP

PROVIDER: S-EPMC3936448 | biostudies-literature | 2014 Feb

REPOSITORIES: biostudies-literature

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Structure of the carboxy-terminal domain of Mycobacterium tuberculosis CarD protein: an essential rRNA transcriptional regulator.

Gangwar Shanti P SP Meena Sita R SR Saxena Ajay K AK

Acta crystallographica. Section F, Structural biology communications 20140121 Pt 2

The CarD protein is highly expressed in mycobacterial strains under basal conditions and is transcriptionally induced during multiple types of genotoxic stress and starvation. The CarD protein binds the β subunit of RNA polymerase and influences gene expression. The disruption of interactions between CarD and the β subunit of RNA polymerase has a significant effect on mycobacterial survival, resistance to stress and pathogenesis. To understand the structure of CarD and its interaction with the β ...[more]

PMID: 24637748

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Project description:CarD is an essential RNA polymerase (RNAP) interacting protein in Mycobacterium tuberculosis that stimulates formation of RNAP-promoter open complexes. CarD plays a complex role in M. tuberculosis growth and virulence that is not fully understood. Therefore, to gain further insight into the role of CarD in M. tuberculosis growth and virulence, we determined the effect of increasing the affinity of CarD for RNAP. Using site-directed mutagenesis guided by crystal structures of CarD bound to RNAP, we identified amino acid substitutions that increase the affinity of CarD for RNAP. Using these substitutions, we show that increasing the affinity of CarD for RNAP increases the stability of the CarD protein in M. tuberculosis In addition, we show that increasing the affinity of CarD for RNAP increases the growth rate in M. tuberculosis without affecting 16S rRNA levels. We further show that increasing the affinity of CarD for RNAP reduces M. tuberculosis virulence in a mouse model of infection despite the improved growth rate in vitro Our findings suggest that the CarD-RNAP interaction protects CarD from proteolytic degradation in M. tuberculosis, establish that growth rate and rRNA levels can be uncoupled in M. tuberculosis and demonstrate that the strength of the CarD-RNAP interaction has been finely tuned to optimize virulence. Mycobacterium tuberculosis, the causative agent of tuberculosis, remains a major global health problem. In order to develop new strategies to battle this pathogen, we must gain a better understanding of the molecular processes involved in its survival and pathogenesis. We have previously identified CarD as an essential transcriptional regulator in mycobacteria. In this study, we detail the effects of increasing the affinity of CarD for RNAP on transcriptional regulation, CarD protein stability, and virulence. These studies expand our understanding of the global transcription regulator CarD, provide insight into how CarD activity is regulated, and broaden our understanding of prokaryotic transcription.

Dataset Information

Structure of the carboxy-terminal domain of Mycobacterium tuberculosis CarD protein: an essential rRNA transcriptional regulator.

Publications

Structure of the carboxy-terminal domain of Mycobacterium tuberculosis CarD protein: an essential rRNA transcriptional regulator.

Similar Datasets

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