Chloroplasts evolved from cyanobacterial endosymbiotic ancestors and their division is a complex process initiated by the assembly of cytoskeletal FtsZ (Filamentous temperature sensitive Z) proteins into a ring structure at the division site (Z-ring). The cyanobacterial Z-ring positioning system (MinCDE proteins) is also conserved in chloroplasts, except that MinC was lost and replaced by the eukaryotic ARC3 (accumulation and replication of chloroplasts). Both MinC and ARC3 act as negative regulators of FtsZ assembly, but ARC3 bears little sequence similarity with MinC. Here, light scattering assays, co-sedimentation, GTPase assay and transmission electron microscopy in conjunction with single-particle analysis have been used to elucidate the structure of ARC3 and its effect on its main target in chloroplast division, FtsZ2. Analysis of FtsZ2 in vitro assembly reactions in the presence and absence of GMPCPP showed that ARC3 promotes FtsZ2 debundling and disassembly of existing filaments in a concentration-dependent manner and requires GTP hydrolysis. Three-dimensional reconstruction of ARC3 revealed an almost circular molecule in which the FtsZ-binding N-terminus and the C-terminal PARC6 (paralog of ARC6)-binding MORN (Membrane Occupation and Recognition Nexus) domain are in close proximity and suggest a model for PARC6-enabled binding of ARC3 to FtsZ2. The latter is corroborated by in vivo data.
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January 2018
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A 3D representation of the filamentous cyanobacteria Anabaena. In this issue, Sein-Echaluce et al. report on the molecular basis for the integration of environmental signals by FurB from Anabaena sp. PCC 7120; for details see pages 151–168.
Research Article|
January 02 2018
Chloroplast division protein ARC3 acts on FtsZ2 by preventing filament bundling and enhancing GTPase activity
Rahamthulla S. Shaik;
Rahamthulla S. Shaik
1Department of Biology, Texas A&M University, College Station, TX 77843, U.S.A.
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Min Woo Sung;
Min Woo Sung
1Department of Biology, Texas A&M University, College Station, TX 77843, U.S.A.
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Stanislav Vitha;
Stanislav Vitha
2Microscopy & Imaging Center, Texas A&M University, College Station, TX 77843, U.S.A.
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Andreas Holzenburg
Andreas Holzenburg
1Department of Biology, Texas A&M University, College Station, TX 77843, U.S.A.
2Microscopy & Imaging Center, Texas A&M University, College Station, TX 77843, U.S.A.
3Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, U.S.A.
4Department of Biomedical Sciences, School of Medicine, University of Texas Rio Grande Valley, Brownsville-Edinburg-Harlingen, TX 78550, U.S.A.
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Biochem J (2018) 475 (1): 99–115.
Article history
Received:
September 10 2017
Revision Received:
November 09 2017
Accepted:
November 10 2017
Accepted Manuscript online:
November 14 2017
Citation
Rahamthulla S. Shaik, Min Woo Sung, Stanislav Vitha, Andreas Holzenburg; Chloroplast division protein ARC3 acts on FtsZ2 by preventing filament bundling and enhancing GTPase activity. Biochem J 15 January 2018; 475 (1): 99–115. doi: https://doi.org/10.1042/BCJ20170697
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