Structural insights into the functional divergence of WhiB-like proteins in Mycobacterium tuberculosis

Authors

• Tao Wan, University of Nebraska-LincolnFollow
• Magdalena HorovaFollow
• Daisy Guiza Beltran, University of Nebraska-LincolnFollow
• Shanren Li, University of Nebraska-Lincoln
• Huey-Xian Wong, University of Nebraska - LincolnFollow
• Li-Mei Zhang, University of Nebraska-Lincoln

Document Type

Article

Date of this Version

7-15-2021

Citation

Mol Cell. 2021 July 15; 81(14): 2887–2900.e5. doi:10.1016/j.molcel.2021.06.002

Comments

public access

Abstract

WhiB7 represents a distinct subclass of transcription factors in the WhiB-Like (Wbl) family, a unique group of iron-sulfur (4Fe-4S] cluster-containing proteins exclusive to the phylum of Actinobacteria. In Mycobacterium tuberculosis (Mtb), WhiB7 interacts with domain 4 of the primary sigma factor (σ_^A4) in the RNA polymerase holoenzyme and activates genes involved in multiple drug resistance and redox homeostasis. Here, we report crystal structures of the WhiB7:σ^A₄ complex alone and bound to its target promoter DNA at 1.55-Å and 2.6-Å resolution, respectively. These structures show how WhiB7 regulates gene expression by interacting with both σ^A₄ and the AT-rich sequence upstream of the –35 promoter DNA via its C-terminal DNA-binding motif, the AT-hook. By combining comparative structural analysis of the two high-resolution σ^A₄-bound Wbl structures with molecular and biochemical approaches, we identify the structural basis of the functional divergence between the two distinct subclasses of Wbl proteins in Mtb.