7EWD image
Entry Detail
PDB ID:
7EWD
Title:
Mycobacterium tuberculosis HigA2 (Form II)
Biological Source:
PDB Version:
Deposition Date:
2021-05-25
Release Date:
2022-03-02
Method Details:
Experimental Method:
Resolution:
3.20 Å
R-Value Free:
0.26
R-Value Work:
0.21
R-Value Observed:
0.21
Space Group:
P 43 21 2
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:Putative antitoxin HigA2
Chain IDs:A, B, C, D
Chain Length:101
Number of Molecules:4
Biological Source:Mycobacterium tuberculosis (strain ATCC 25618 / H37Rv)
Ligand Molecules
Primary Citation
Chasing the structural diversity of the transcription regulator Mycobacterium tuberculosis HigA2.
Iucrj 8 823 832 (2021)
PMID: 34584743 DOI: 10.1107/S2052252521007715

Abstact

Transcription factors are the primary regulators of gene expression and recognize specific DNA sequences under diverse physiological conditions. Although they are vital for many important cellular processes, it remains unclear when and how transcription factors and DNA interact. The antitoxin from a toxin-antitoxin system is an example of negative transcriptional autoregulation: during expression of the cognate toxin it is suppressed through binding to a specific DNA sequence. In the present study, the antitoxin HigA2 from Mycobacterium tuberculosis M37Rv was structurally examined. The crystal structure of M. tuberculosis HigA2 comprises three sections: an N-terminal autocleavage region, an α-helix bundle which contains an HTH motif, and a C-terminal β-lid. The N-terminal region is responsible for toxin binding, but was shown to cleave spontaneously in its absence. The HTH motif performs a key role in DNA binding, with the C-terminal β-lid influencing the interaction by mediating the distance between the motifs. However, M. tuberculosis HigA2 exhibits a unique coordination of the HTH motif and no DNA-binding activity is detected. Three crystal structures of M. tuberculosis HigA2 show a flexible alignment of the HTH motif, which implies that the motif undergoes structural rearrangement to interact with DNA. This study reveals the molecular mechanisms of how transcription factors interact with partner proteins or DNA.

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Primary Citation of related structures