Structure of a TOC-TIC supercomplex spanning two chloroplast envelope membranes

Jin, Zeyu; Wan, Li; Zhang, Yuqi; Li, Xuecheng; Cao, Yong; Liu, Haobin; Fan, Shengyao; Cao, Du; Wang, Zhengmao; Li, Xiaobo; Pan, Junmin; Dong, Meng‐Qiu; Wu, Jianping; Zhen, Yan

doi:10.1016/j.cell.2022.10.030

Cited by 37 publications

(27 citation statements)

References 95 publications

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“…Confirmation of edited sequences is generally established by PCR and sequencing and facilitated by the introduction of drug resistance cassettes (for knock‐in genes) and co‐targeting of selectable mutations (Akella et al, 2021; Dhokane et al, 2021; Guzman‐Zapata et al, 2019,). Recent applications of CRISPR technology to Chlamydomonas have allowed for endogenous tagging of proteins with either an epitope or a fluorophore and precise sequence editing to generate predicted lesions (Jin et al, 2022; Kubo et al, 2023; Nievergelt et al, 2022).…”

Section: Crispr‐cas9mentioning

confidence: 99%

Chlamydomonas: Fast tracking from genomics

Findinier

Grossman

2023

Journal of Phycology

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Elucidating biological processes has relied on the establishment of model organisms, many of which offer advantageous features such as rapid axenic growth, extensive knowledge of their physiological features and gene content, and the ease with which they can be genetically manipulated. The unicellular green alga Chlamydomonas reinhardtii has been an exemplary model that has enabled many scientific breakthroughs over the decades, especially in the fields of photosynthesis, cilia function and biogenesis, and the acclimation of photosynthetic organisms to their environment. Here, we discuss recent molecular/technological advances that have been applied to C. reinhardtii and how they have further fostered its development as a “flagship” algal system. We also explore the future promise of this alga in leveraging advances in the fields of genomics, proteomics, imaging, and synthetic biology for addressing critical future biological issues.

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Section: Crispr‐cas9mentioning

confidence: 99%

Chlamydomonas: Fast tracking from genomics

Findinier

Grossman

2023

Journal of Phycology

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“…TOC75 is a ß-barrel protein, homologous with the OEP80 gene family in bacteria, which is thought to form the channel of the translocase with a pore size of 30-35Å and is capable of importing folded proteins (Inoue and Potter, 2004;Ganesan and Theg, 2019). New evidence in green algae suggests TOC75 forms a hybrid ßbarrel pore in conjunction with TOC120 to conduct preproteins (Jin et al, 2022), though the prevalence of this configuration is unknown. TOC33 and TOC34, the two major TOC34 paralogs, represent the smaller GTPase receptors.…”

Section: Toc Componentsmentioning

confidence: 99%

Understanding protein import in diverse non-green plastids

Christian

Labbancz²,

Usadel³

et al. 2023

Front. Genet.

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The spectacular diversity of plastids in non-green organs such as flowers, fruits, roots, tubers, and senescing leaves represents a Universe of metabolic processes in higher plants that remain to be completely characterized. The endosymbiosis of the plastid and the subsequent export of the ancestral cyanobacterial genome to the nuclear genome, and adaptation of the plants to all types of environments has resulted in the emergence of diverse and a highly orchestrated metabolism across the plant kingdom that is entirely reliant on a complex protein import and translocation system. The TOC and TIC translocons, critical for importing nuclear-encoded proteins into the plastid stroma, remain poorly resolved, especially in the case of TIC. From the stroma, three core pathways (cpTat, cpSec, and cpSRP) may localize imported proteins to the thylakoid. Non-canonical routes only utilizing TOC also exist for the insertion of many inner and outer membrane proteins, or in the case of some modified proteins, a vesicular import route. Understanding this complex protein import system is further compounded by the highly heterogeneous nature of transit peptides, and the varying transit peptide specificity of plastids depending on species and the developmental and trophic stage of the plant organs. Computational tools provide an increasingly sophisticated means of predicting protein import into highly diverse non-green plastids across higher plants, which need to be validated using proteomics and metabolic approaches. The myriad plastid functions enable higher plants to interact and respond to all kinds of environments. Unraveling the diversity of non-green plastid functions across the higher plants has the potential to provide knowledge that will help in developing climate resilient crops.

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“…TOC159 and its three homologs in Arabidopsis (atTOC120, −132, −90) possess a central GTPase (G-) domain, a C-terminal membrane-anchoring (M-) domain, and a N-terminal acidic (A-) domain at the N-terminus ( Kubis et al, 2004 ). The M-domain has now been shown to take on a ß-barrel structure and associate with TOC75 to form a large hybrid channel at the outer chloroplast membrane ( Jin et al, 2022 ; Liu et al, 2023 ). The A-domains in the four Arabidopsis isoforms of TOC159 are much more divergent than the G- and M-domains and appear to play a role in pre-protein specificity ( Agne et al, 2010 ).…”

Section: Protein Translocation Into the Chloroplastmentioning

confidence: 99%

“…On the other hand, an alternative stromal motor has been proposed that consists of a 2-MDa ycf2/FtsH1 complex that also has predicted ATP hydrolysis activity ( Kikuchi et al, 2018 ). However, the respective significance of the two proposed motor systems has not been evaluated so far, and neither of the two systems were observed in the currently available Cryo-EM structures ( Jin et al, 2022 ; Liu et al, 2023 ).…”

Section: Protein Translocation Into the Chloroplastmentioning

confidence: 99%

“…It would now be highly interesting to study the cryo-EM structure of the TOC-TIC complex in association with a preprotein and its transit peptide to gain a complete understanding of the import process. Also, the recent cryo-EM structures failed to reveal the cytosolic GTPase domains of the TOC34 and −159 ( Jin et al, 2022 ; Liu et al, 2023 ) that play a central role in transit peptide recognition. The GTPase domains should remain a key target in future structural work.…”

Section: Conclusion and Future Perspectivesmentioning

confidence: 99%

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The journey of preproteins across the chloroplast membrane systems

et al. 2023

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The photosynthetic capacity of chloroplasts is vital for autotrophic growth in algae and plants. The origin of the chloroplast has been explained by the endosymbiotic theory that proposes the engulfment of a cyanobacterium by an ancestral eukaryotic cell followed by the transfer of many cyanobacterial genes to the host nucleus. As a result of the gene transfer, the now nuclear-encoded proteins acquired chloroplast targeting peptides (known as transit peptides; transit peptide) and are translated as preproteins in the cytosol. Transit peptides contain specific motifs and domains initially recognized by cytosolic factors followed by the chloroplast import components at the outer and inner envelope of the chloroplast membrane. Once the preprotein emerges on the stromal side of the chloroplast protein import machinery, the transit peptide is cleaved by stromal processing peptidase. In the case of thylakoid-localized proteins, cleavage of the transit peptides may expose a second targeting signal guiding the protein to the thylakoid lumen or allow insertion into the thylakoid membrane by internal sequence information. This review summarizes the common features of targeting sequences and describes their role in routing preproteins to and across the chloroplast envelope as well as the thylakoid membrane and lumen.

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Structure of a TOC-TIC supercomplex spanning two chloroplast envelope membranes

Cited by 37 publications

References 95 publications

Chlamydomonas: Fast tracking from genomics

Chlamydomonas: Fast tracking from genomics

Understanding protein import in diverse non-green plastids

The journey of preproteins across the chloroplast membrane systems

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