Heme binds to an intrinsically disordered region of Bach2 and alters its conformation

Miki Watanabe-Matsui, Takashi Matsumoto, Toshitaka Matsui, Masao Ikeda-Saito, Akihiko Muto, Kazutaka Murayama, Kazuhiko Igarashi

Research output: Contribution to journalArticlepeer-review

31 Citations (Scopus)


The transcriptional repressor Bach2 regulates humoral and cellular immunity, including antibody class switching. It possesses a basic leucine zipper domain that mediates DNA binding. Heme inhibits the DNA-binding activity of Bach2 in vitro and induces the degradation of Bach2 in B cells. However, the structural basis of the heme-Bach2 interaction has not been identified. Spectroscopic analyses revealed that Bach2331-520 is the heme-binding domain, as it includes three Cys-Pro motifs known to be important for heme binding. Heme-titration experiments demonstrated the presence of 5- and 6-coordinated heme-binding modes. Circular dichroism measurements indicated that Bach2331-520 exists mostly in a random-coil conformation. However, dynamic light scattering analyses showed that, upon heme binding to Bach2331-520, this region becomes denatured at a lower temperature, as compared with unbound Bach2331-520. In addition, small-angle X-ray scattering and chemical modification analyses revealed that heme binding induces conformational alterations within the unstructured region. A GAL4-based luciferase assay in 293T cells showed that heme alters the protein interactions mediated by Bach2331-520. These observations suggested that the unstructured region of Bach2 is important for heme binding, and consequently for its functional regulation.

Original languageEnglish
Pages (from-to)25-31
Number of pages7
JournalArchives of Biochemistry and Biophysics
Publication statusPublished - 2015 Jan 1


  • Chemical modification
  • Conformation change
  • Heme binding
  • Intrinsically disordered protein
  • Small-angle X-ray scattering


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