Poster Presentation 21st International Conference on Biological Inorganic Chemistry 2025

Structural-functional analysis of heme-containing oxygen sensor protein HemAT in chemotaxis regulatory system (#504)

Rei Tohda 1 , Norifumi Muraki 2 , Seiki Baba 3 , Hideo Okumura 3 , Yoshiaki Kawano 4 , Takeshi Yokoyama 5 , Shigetoshi Aono 6
  1. University of Hyogo, Ako-gun, Hyogo, Japan
  2. Faculty of Science and Technology, Keio University, Yokohama, Kanagawa, Japan
  3. Structural Biology Division, Japan Synchrotron Radiation Research Institute, Sayo-gun, Hyogo, Japan
  4. Advanced Photon Technology Division, RIKEN SPring-8 Center, Sayo-gun, Hyogo, Japan
  5. Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi, Japan
  6. Department of Creative Research, Exploratory Research Center on Life and Living Systems, National Institutes of Natural Sciences, Okazaki, Aichi, Japan

In bacteria and cells, receptor proteins are essential for sensing signals to regulate chemotaxis. The representative receptor protein for regulating aerotaxis (chemotaxis toward O2) in bacteria is HemAT1. HemAT is a heme-containing signal transducer protein that regulates the chemotaxis in bacteria, which detects oxygen molecules by its heme. HemAT consists of two domains, the N-terminal sensor domain, and the C-terminal signaling domain. The sensor domain of HemAT shows structural homology to myoglobin, and the signaling domain is similar to the MCP family of bacterial chemoreceptors. The signaling domain transmits the sensing signal from the sensor domain to Che proteins (CheA, CheW, and CheY) to control the regulation of flagella rotation in bacteria. However, the oxygen sensing mechanism and its signaling mechanism are not well understood because of the missing structural information of HemAT and HemAT:CheA:CheW:CheY complex.

To understand the sensing and signaling mechanisms of the HemAT:CheA:CheW:CheY complex, we aim to determine the structures of the O2-binding and redox forms of HemAT and the HemAT:CheA:CheW:CheY complex using X-ray crystallography and cryo-electron microscopy (Cryo-EM). We have successfully solved the O2-binding and redox forms of the HemAT sensor domain at 2.36 Å resolution and observed dynamic changes in the proximal region of HemAT. In this poster presentation, we will show the structures of HemAT sensor domain and HemAT:CheA:CheW complex, and discuss the mechanisms based on these findings.

  1. (1) Hou, S.; Larsen, R. W.; Boudko, D.; Riley, C. W.; Karatan, E.; Zimmer, M.; Ordal, G. W.; Alam, M. Myoglobin-like Aerotaxis Transducers in Archaea and Bacteria/Nature, 2000, 403, 6769, 540–544.