Structures of the LPOR–Chlide Complexes Imply the Basis of Membrane Remodeling and a Photocatalytic Mechanism
Abstract
Flowering plants rely on the photocatalytic enzyme light-dependent protochlorophyllide oxidoreductase (LPOR) to synthesize chlorophyllide (Chlide), a chlorophyll intermediate, and at the same time to remodel lipid membranes into the cubic phase required for chloroplast development. Yet neither the mechanism of this light-driven catalysis nor the structural basis of its membrane remodeling activity is well understood, largely due to the lack of high-resolution structural information. To address these questions, we analyzed Chlide:LPOR:NADPH oligomeric assemblies by cryo-electron microscopy. Eleven maps were obtained, enabling the reconstruction of nine distinct LPOR oligomer models. Most assemblies adopt helical or stacked-ring forms, whereas one displays a segmented string-of-dimers architecture, representing a previously unobserved structural organization. Strings of LPOR dimers induce distinct periodic deformations of the lipid bilayer that stabilize multiple complex architectures. These architectures are maintained by three different inter-string interfaces occurring in various combinations. The plasticity of these interactions suggest that the filaments are capable of twisting and sliding relative to each other. Our highest-resolution map (2.55 Å) provided a detailed view of the pigment-binding site, revealing a water channel that connects the central magnesium ion of the pigment to the bulk solvent. Unexpectedly, the propionate group of the pigment protrudes out of the porphyrin plane and arches back toward NADPH, ideally positioned for hydride transfer. These structural insights allowed us to propose a novel reaction mechanism for LPOR photocatalysis. Together, our data highlight the critical role of Chlide:LPOR:NADPH complexes in delaying prolamellar body disassembly and point to their possible regulatory function in mature leaves.
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BibTeX
@article{gabruk2026structures,
title = {{Structures of the LPOR–Chlide Complexes Imply the Basis of Membrane Remodeling and a Photocatalytic Mechanism}},
author = {Michał Gabruk and Ambroise Desfosses and Leandro Farias Estrozi and Sebastian Pintscher and Michał Rawski and Grzegorz Ważny and Agnieszka Garbacz and Mateusz Zbyradowski and Jerzy Kruk and Leszek Fiedor},
journal = {Nature Communications},
year = {2026},
month = aug,
doi = {10.1038/s41467-026-76316-7},
url = {https://hal.science/hal-05764343v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Structures of the LPOR–Chlide Complexes Imply the Basis of Membrane Remodeling and a Photocatalytic Mechanism
AU - Michał Gabruk
AU - Ambroise Desfosses
AU - Leandro Farias Estrozi
AU - Sebastian Pintscher
AU - Michał Rawski
AU - Grzegorz Ważny
AU - Agnieszka Garbacz
AU - Mateusz Zbyradowski
AU - Jerzy Kruk
AU - Leszek Fiedor
PY - 2026
DA - 2026/08/05
JO - Nature Communications
DO - 10.1038/s41467-026-76316-7
UR - https://hal.science/hal-05764343v1
AB - Flowering plants rely on the photocatalytic enzyme light-dependent protochlorophyllide oxidoreductase (LPOR) to synthesize chlorophyllide (Chlide), a chlorophyll intermediate, and at the same time to remodel lipid membranes into the cubic phase required for chloroplast development. Yet neither the mechanism of this light-driven catalysis nor the structural basis of its membrane remodeling activity is well understood, largely due to the lack of high-resolution structural information. To address these questions, we analyzed Chlide:LPOR:NADPH oligomeric assemblies by cryo-electron microscopy. Eleven maps were obtained, enabling the reconstruction of nine distinct LPOR oligomer models. Most assemblies adopt helical or stacked-ring forms, whereas one displays a segmented string-of-dimers architecture, representing a previously unobserved structural organization. Strings of LPOR dimers induce distinct periodic deformations of the lipid bilayer that stabilize multiple complex architectures. These architectures are maintained by three different inter-string interfaces occurring in various combinations. The plasticity of these interactions suggest that the filaments are capable of twisting and sliding relative to each other. Our highest-resolution map (2.55 Å) provided a detailed view of the pigment-binding site, revealing a water channel that connects the central magnesium ion of the pigment to the bulk solvent. Unexpectedly, the propionate group of the pigment protrudes out of the porphyrin plane and arches back toward NADPH, ideally positioned for hydride transfer. These structural insights allowed us to propose a novel reaction mechanism for LPOR photocatalysis. Together, our data highlight the critical role of Chlide:LPOR:NADPH complexes in delaying prolamellar body disassembly and point to their possible regulatory function in mature leaves.
SN - 2041-1723
SN - 2041-1723
ER -