title: Arabidopsis CURVATURE THYLAKOID1 proteins modify thylakoid architecture by inducing membrane curvature.
abstract: Chloroplasts of land plants characteristically contain grana, cylindrical stacks of thylakoid membranes. A granum consists of a core of appressed membranes, two stroma-exposed end membranes, and margins, which connect pairs of grana membranes at their lumenal sides. Multiple forces contribute to grana stacking, but it is not known how the extreme curvature at margins is generated and maintained. We report the identification of the CURVATURE THYLAKOID1 (CURT1) protein family, conserved in plants and cyanobacteria. The four Arabidopsis thaliana CURT1 proteins (CURT1A, B, C, and D) oligomerize and are highly enriched at grana margins. Grana architecture is correlated with the CURT1 protein level, ranging from flat lobe-like thylakoids with considerably fewer grana margins in plants without CURT1 proteins to an increased number of membrane layers (and margins) in grana at the expense of grana diameter in overexpressors of CURT1A. The endogenous CURT1 protein in the cyanobacterium Synechocystis sp PCC6803 can be partially replaced by its Arabidopsis counterpart, indicating that the function of CURT1 proteins is evolutionary conserved. In vitro, Arabidopsis CURT1A proteins oligomerize and induce tubulation of liposomes, implying that CURT1 proteins suffice to induce membrane curvature. We therefore propose that CURT1 proteins modify thylakoid architecture by inducing membrane curvature at grana margins.
authors.affiliation: Plant Molecular Biology (Botany), Department Biology I, Ludwig-Maximilians-Universität München, 81252 Planegg-Martinsried, Germany.
authors.forename: Ute
authors.initials: U
authors.lastname: Armbruster
authors.forename: Mathias
authors.initials: M
authors.lastname: Labs
authors.forename: Mathias
authors.initials: M
authors.lastname: Pribil
authors.forename: Stefania
authors.initials: S
authors.lastname: Viola
authors.forename: Wenteng
authors.initials: W
authors.lastname: Xu
authors.forename: Michael
authors.initials: M
authors.lastname: Scharfenberg
authors.forename: Alexander P
authors.initials: AP
authors.lastname: Hertle
authors.forename: Ulrike
authors.initials: U
authors.lastname: Rojahn
authors.forename: Poul Erik
authors.initials: PE
authors.lastname: Jensen
authors.forename: Fabrice
authors.initials: F
authors.lastname: Rappaport
authors.forename: Pierre
authors.initials: P
authors.lastname: Joliot
authors.forename: Peter
authors.initials: P
authors.lastname: Dörmann
authors.forename: Gerhard
authors.initials: G
authors.lastname: Wanner
authors.forename: Dario
authors.initials: D
authors.lastname: Leister
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism* / Q000648:ultrastructure; D015151:Immunoblotting; D007425:Intracellular Membranes / Q000378:metabolism* / Q000648:ultrastructure; D008055:Lipids / Q000032:analysis; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D009154:Mutation; D010766:Phosphorylation; D010788:Photosynthesis; D010802:Phylogeny; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D011510:Proteolipids / Q000378:metabolism / Q000648:ultrastructure; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D020524:Thylakoids / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D029681:Arabidopsis Proteins; D008055:Lipids; D011510:Proteolipids; C020485:proteoliposomes; D002734:Chlorophyll