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A Janus-Faced IM30 Ring Involved in Thylakoid Membrane Fusion Is Assembled from IM30 Tetramers

Michael Saur1, Raoul Hennig2, Phoebe Young3

  • 1Institut für Molekulare Physiologie, Johannes Gutenberg-Universität Mainz, 55128 Mainz, Germany.

Structure (London, England : 1993)
|August 15, 2017
PubMed

Insights

Inner membrane protein IM30 (30 kDa) drives membrane fusion by forming Janus-faced rings. Mutating key regions disrupts fusion, revealing IM30

Area of Science:

  • Cell Biology
  • Membrane Biology
  • Protein Structure and Function

Background:

  • Thylakoid membrane biogenesis and dynamics involve membrane fusion.
  • The inner membrane-associated protein of 30 kDa (IM30) is implicated in membrane fusion.
  • The precise mechanism by which IM30 induces membrane fusion remains largely unknown.

Purpose of the Study:

  • To elucidate the structural basis of IM30-mediated membrane fusion.
  • To investigate the role of specific IM30 regions in membrane binding and fusion.

Main Methods:

  • 3D reconstruction of IM30 rings.
  • Analysis of IM30 loop 2 and helix 7 mutants.
  • Assessment of membrane binding and fusogenic activity.

Main Results:

  • IM30 monomers assemble into tetramers and then oligomeric rings of varying sizes.
  • IM30 loop 2 is located at the bottom of the ring and is crucial for fusogenic activity, though not for membrane binding.
  • Helix 7, responsible for membrane binding, is located at the top of the IM30 ring.
  • Mutations in loop 2 abolish fusogenic activity.

Conclusions:

  • IM30 functions as a two-sided complex, connecting opposing membranes.
  • The Janus-faced nature of the IM30 ring, with distinct functional sides, is essential for mediating membrane fusion.
Keywords:
PspAVipp1membrane biogenesismembrane fusionstructurethylakoid membrane

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