bims-mimbat Biomed News
on Mitochondrial metabolism in brown adipose tissue
Issue of 2025–05–11
two papers selected by
José Carlos de Lima-Júnior, Washington University
  1. Cryo-EM of Mitochondrial Complex I and ATP Synthase.
  2. A short intrinsically disordered region at KtrB's N-terminus facilitates allosteric regulation of K+ channel KtrAB.
  1. Annu Rev Biophys. 2025 May;54(1): 209-226
    Cryo-EM of Mitochondrial Complex I and ATP Synthase.
    Werner Kühlbrandt, Luis A M Carreira, Özkan Yildiz.
      Cryo-electron microscopy (cryo-EM) is the method of choice for investigating the structures of membrane protein complexes at high resolution under near-native conditions. This review focuses on recent cryo-EM work on mitochondrial complex I and ATP synthase. Single-particle cryo-EM structures of complex I from mammals, plants, and fungi extending to a resolution of 2 Å show different functional states, indicating consistent conformational changes of loops near the Q binding site, clusters of internal water molecules in the membrane arm, and an α-π transition in a membrane-spanning helix that opens and closes the proton transfer path. Cryo-EM structures of ATP synthase dimers from mammalian, yeast, and Polytomella mitochondria show several rotary states at a resolution of 2.7 to 3.5 Å. The new structures of complex I and ATP synthase are important steps along the way toward understanding the detailed molecular mechanisms of both complexes. Cryo-electron tomography and subtomogram averaging have the potential to resolve their high-resolution structures in situ.
    Keywords:  ATP synthase; complex I; cryo-electron microscopy; cryo-electron tomography; mitochondria; respiratory chain
    DOI:  https://doi.org/10.1146/annurev-biophys-060724-110838
  2. Nat Commun. 2025 May 07. 16(1): 4252
    A short intrinsically disordered region at KtrB's N-terminus facilitates allosteric regulation of K+ channel KtrAB.
    Janina Stautz, David Griwatz, Susann Kaltwasser, Ahmad Reza Mehdipour, Sophie Ketter, Celina Thiel, Dorith Wunnicke, Marina Schrecker, Deryck J Mills, Gerhard Hummer, Janet Vonck, Inga Hänelt.
      K+ homeostasis is crucial for bacterial survival. The bacterial K+ channel KtrAB is regulated by the binding of ADP and ATP to the cytosolic RCK subunits KtrA. While the ligand-induced conformational changes in KtrA are well described, the transmission to the gating regions within KtrB is not understood. Here, we present a cryo-EM structure of the ADP-bound, inactive KtrAB complex from Vibrio alginolyticus, which resolves part of KtrB's N termini. They are short intrinsically disordered regions (IDRs) located at the interface of KtrA and KtrB. We reveal that these IDRs play a decisive role in ATP-mediated channel opening, while the closed ADP-bound state does not depend on the N-termini. We propose an allosteric mechanism, in which ATP-induced conformational changes within KtrA trigger an interaction of KtrB's N-terminal IDRs with the membrane, stabilizing the active and conductive state of KtrAB.
    DOI:  https://doi.org/10.1038/s41467-025-59546-z
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