Polypeptide Transport-Associated Domains of the Toc75 Channel Protein Are Located in the Intermembrane Space of Chloroplasts

Chen, Yih-Lin; Chen, Lih‐Jen; Li, Hsou‐min

doi:10.1104/pp.16.00919

Cited by 33 publications

(29 citation statements)

References 42 publications

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“…All antibodies used were raised in rabbits. Five of the antibodies used have been described previously: antibodies against Arabidopsis Toc159 and pea Toc34 (Tu et al ., ), Arabidopsis Tic20‐I (At1g04940) (Teng et al ., ), Arabidopsis Toc75 POTRA domains (Chen et al ., ), and Arabidopsis Tic56 (Köhler et al ., ). The antibody against pea Toc75 POTRA‐1 domain was purchased from Agrisera (AS08 345).…”

Section: Methodsmentioning

confidence: 99%

Stable megadalton TOC–TIC supercomplexes as major mediators of protein import into chloroplasts

Chen

2017

The Plant Journal

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SUMMARYPreproteins are believed to be imported into chloroplasts through membrane contact sites where the translocon complexes of the outer (TOC) and inner (TIC) envelope membranes are assembled together. However, a single TOC-TIC supercomplex containing preproteins undergoing active import has not yet been directly observed. We optimized the blue native polyacrylamide gel electrophoresis (PAGE) (BN-PAGE) system to detect and resolve megadalton (MD)-sized complexes. Using this optimized system, the outer-membrane channel Toc75 from pea chloroplasts was found in at least two complexes: the 880-kD TOC complex and a previously undetected 1-MD complex. Two-dimensional BN-PAGE immunoblots further showed that Toc75, Toc159, Toc34, Tic20, Tic56 and Tic110 were all located in the 880-kD to 1.3-MD region. During active preprotein import, preproteins were transported mostly through the 1-MD complex and a smaller amount of preproteins was also detected in a complex of 1.25 MD. Antibody-shift assays showed that the 1-MD complex is a TOC-TIC supercomplex containing at least Toc75, Toc159, Toc34 and Tic110. Results from crosslinking and import with Arabidopsis chloroplasts suggest that the 1.25-MD complex is also a supercomplex. Our data provide direct evidence supporting that chloroplast preproteins are imported through TOC-TIC supercomplexes, and also provide the first size estimation of these supercomplexes. Furthermore, unlike in mitochondria where translocon supercomplexes are only transiently assembled during preprotein import, in chloroplasts at least some of the supercomplexes are preassembled stable structures.

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Section: Methodsmentioning

confidence: 99%

Stable megadalton TOC–TIC supercomplexes as major mediators of protein import into chloroplasts

Chen

2017

The Plant Journal

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“…Toc159 and Toc34 share a highly conserved GTP-binding domain that initially recognize the chloroplast targeting peptide (Kouranov and Schnell, 1997;Keegstra and Froehlich, 1999;Chen et al, 2000;Sveshnikova et al, 2000;Schnell, 2002, 2006;Becker et al, 2004;Dutta et al, 2009). The polypeptide transport-associated (POTRA) domains of Toc75 orient toward the intermembrane space and prevent preproteins from misfolding there (Chen et al, 2016;Paila et al, 2016;Richardson et al, 2017). Moreover, Tic22 is a chaperone in the intermembrane space and facilitates the continuity of precursor translocation between the TOC and TIC channels (Richardson et al, 2017).…”

Section: Chloroplast Protein Quality Controlmentioning

confidence: 99%

Sensitivity and Responses of Chloroplasts to Heat Stress in Plants

2020

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Increased temperatures caused by global warming threaten agricultural production, as warmer conditions can inhibit plant growth and development or even destroy crops in extreme circumstances. Extensive research over the past several decades has revealed that chloroplasts, the photosynthetic organelles of plants, are highly sensitive to heat stress, which affects a variety of photosynthetic processes including chlorophyll biosynthesis, photochemical reactions, electron transport, and CO 2 assimilation. Important mechanisms by which plant cells respond to heat stress to protect these photosynthetic organelles have been identified and analyzed. More recent studies have made it clear that chloroplasts play an important role in inducing the expression of nuclear heat-response genes during the heat stress response. In this review, we summarize these important advances in plant-based research and discuss how the sensitivity, responses, and signaling roles of chloroplasts contribute to plant heat sensitivity and tolerance.

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“…Ertel et al 2005;Habib et al 2007;Kutik et al 2008). Similar to the POTRA domains of its proteobacterial ancestor, the single POTRA domain of Sam50 is exposed to the intermembrane space (Habib et al 2007), while the localisation of the three POTRA domains of Toc75 is still under debate (Sommer et al 2011;Chen et al 2016).…”

Section: Introductionmentioning

confidence: 99%

The outer membrane Omp85‐like protein P39 influences metabolic homeostasis in mature Arabidopsis thaliana

et al. 2018

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The Omp85 proteins form a large membrane protein family in bacteria and eukaryotes. Omp85 proteins are composed of a C-terminal β-barrel-shaped membrane domain and one or more N-terminal polypeptide transport-associated (POTRA) domains. However, Arabidopsis thaliana contains two genes coding for Omp85 proteins without a POTRA domain. One gene is designated P39, according to the molecular weight of the encoded protein. The protein is targeted to plastids and it was established that p39 has electrophysiological properties similar to other Omp85 family members, particularly to that designated as Toc75V/Oep80. We analysed expression of the gene and characterised two T-DNA insertion mutants, focusing on alterations in photosynthetic activity, plastid ultrastructure, global expression profile and metabolome. We observed pronounced expression of P39, especially in veins. Mutants of P39 show growth aberrations, reduced photosynthetic activity and changes in plastid ultrastructure, particularly in the leaf tip. Further, they display global alteration of gene expression and metabolite content in leaves of mature plants. We conclude that the function of the plastid-localised and vein-specific Omp85 family protein p39 is important, but not essential, for maintenance of metabolic homeostasis of full-grown A. thaliana plants. Further, the function of p39 in veins influences the functionality of other plant tissues. The link connecting p39 function with metabolic regulation in mature A. thaliana is discussed.

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Polypeptide Transport-Associated Domains of the Toc75 Channel Protein Are Located in the Intermembrane Space of Chloroplasts

Cited by 33 publications

References 42 publications

Stable megadalton TOC–TIC supercomplexes as major mediators of protein import into chloroplasts

Stable megadalton TOC–TIC supercomplexes as major mediators of protein import into chloroplasts

Sensitivity and Responses of Chloroplasts to Heat Stress in Plants

The outer membrane Omp85‐like protein P39 influences metabolic homeostasis in mature Arabidopsis thaliana

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