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

作者：Saur Michael; Hennig Raoul; Young Phoebe; Rusitzka Kristiane; Hellmann Nadja; Heidrich Jennifer; Morgner Nina; Markl Juergen; Schneider Dirk^*

来源：Structure, 2017, 25(9): 1380-+.

DOI：10.1016/j.str.2017.07.001

Biogenesis and dynamics of thylakoid membranes likely involves membrane fusion events. Membrane attachment of the inner membrane-associated protein of 30 kDa (IM30) affects the structure of the lipid bilayer, finally resulting in membrane fusion. Yet, how IM30 triggers membrane fusion is largely unclear. IM30 monomers pre-assemble into stable tetrameric building blocks, which further align to form oligomeric ring structures, and differently sized IM30 rings bind to membranes. Based on a 3D reconstruction of IM30 rings, we locate the IM30 loop 2 region at the bottom of the ring and show intact membrane binding but missing fusogenic activity of loop 2 mutants. However, helix 7, which has recently been shown to mediate membrane binding, was located at the oppossite, top side of IM30 rings. We propose that a two-sided IM30 ring complex connects two opposing membranes, finally resulting in membrane fusion. Thus, IM30-mediated membrane fusion requires a Janus-faced IM30 ring.

• 出版日期2017-9-5