Differential Age-Dependent Import Regulation by Signal Peptides

Teng, Yi-Shan; Chan, Po-Ting; Li, Hsou‐min

doi:10.1371/journal.pbio.1001416

Cited by 59 publications

(67 citation statements)

References 50 publications

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“…For example, cpHsc70 interacts with the N-terminal motif of TPs, which has a moderate hydrophobicity conferred by a few hydrophobic amino acids (Lee et al, 2008;Chotewutmontri et al, 2012;Chotewutmontri and Bruce, 2015). A recent study by Teng et al (2012) also supports this notion; they showed that preproteins with two consecutive basic residues are actively imported into older chloroplasts, whereas those with two consecutive acidic residues are not. The two mechanisms may not be mutually exclusive, but are utilized depending on the situation or the specific translocon component(s) involved.…”

Section: Discussionmentioning

confidence: 90%

Sequence Motifs in Transit Peptides Act as Independent Functional Units and Can Be Transferred to New Sequence Contexts

et al. 2015

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A large number of nuclear-encoded proteins are imported into chloroplasts after they are translated in the cytosol. Import is mediated by transit peptides (TPs) at the N termini of these proteins. TPs contain many small motifs, each of which is critical for a specific step in the process of chloroplast protein import; however, it remains unknown how these motifs are organized to give rise to TPs with diverse sequences. In this study, we generated various hybrid TPs by swapping domains between Rubisco small subunit (RbcS) and chlorophyll a/b-binding protein, which have highly divergent sequences, and examined the abilities of the resultant TPs to deliver proteins into chloroplasts. Subsequently, we compared the functionality of sequence motifs in the hybrid TPs with those of wild-type TPs. The sequence motifs in the hybrid TPs exhibited three different modes of functionality, depending on their domain composition, as follows: active in both wild-type and hybrid TPs, active in wild-type TPs but inactive in hybrid TPs, and inactive in wild-type TPs but active in hybrid TPs. Moreover, synthetic TPs, in which only three critical motifs from RbcS or chlorophyll a/bbinding protein TPs were incorporated into an unrelated sequence, were able to deliver clients to chloroplasts with a comparable efficiency to RbcS TP. Based on these results, we propose that diverse sequence motifs in TPs are independent functional units that interact with specific translocon components at various steps during protein import and can be transferred to new sequence contexts.

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Section: Discussionmentioning

confidence: 90%

Sequence Motifs in Transit Peptides Act as Independent Functional Units and Can Be Transferred to New Sequence Contexts

et al. 2015

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“…The TPs were clustered into nine groups based on their H70BS patterns within the first 80 aa (TP and part of mature protein sequence) using Hierarchical clustering. These groups show pronounced differences in the position of their highest affinity, which varied from position 5 to 70 (5,10,17,23,32,46,52,58, and 70 for groups 1-9, respectively). This fairly even distribution raised a concern that the H70BS was randomly distributed.…”

Section: Resultsmentioning

confidence: 99%

“…Using a clustering algorithm, we can group these TPs into nine clusters where the position of the strongest H70BS is located in different regions. How this H70BS placement functions in relation to the other identified motifs (15,18) and contributes to a general TP design (21,57,58) will be the subject for further study. It is now clear that only three clusters of the TPs have a strongest H70BS within their N-ter 20 aa and together represent 32% of the TPs.…”

Section: Discussionmentioning

confidence: 99%

Non-native, N-terminal Hsp70 Molecular Motor Recognition Elements in Transit Peptides Support Plastid Protein Translocation

Chotewutmontri

Bruce

2015

Journal of Biological Chemistry

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Background: Transit peptides direct the import of the majority of chloroplast-destined proteins into chloroplasts. Results: Multiple unrelated Hsp70 recognition elements are able to substitute for the translocation determinant domain of transit peptides. Conclusion:The majority of transit peptides utilize Hsp70-interacting property to initiate import. Significance: This finding expands the mechanistic view of the chloroplast protein import process.

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“…As shown in Figure 5B, the RidA-GFP fusion protein was found to localize exclusively to chlorophyll-containing chloroplasts in both guard and mesophyll cells. Notably, in mesophyll cells, the RidA-GFP fusion seemed more abundant in smaller chloroplasts than larger ones ( Figure 5B, lower panel), suggesting that, like certain other chloroplast proteins, the targeting of RidA may be influenced by chloroplast age, import capacity, and/or metabolic activity (Kessler and Schnell, 2009;Teng et al, 2012). The Thr dehydratase-GFP fusion protein also localized exclusively to chloroplasts in Arabidopsis mesophyll cells ( Figure 5C).…”

Section: Rida and Thr Dehydratase Are Plastid-targetedmentioning

confidence: 95%

Arabidopsis and Maize RidA Proteins Preempt Reactive Enamine/Imine Damage to Branched-Chain Amino Acid Biosynthesis in Plastids

et al. 2014

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RidA (for Reactive Intermediate Deaminase A) proteins are ubiquitous, yet their function in eukaryotes is unclear. It is known that deleting Salmonella enterica ridA causes Ser sensitivity and that S. enterica RidA and its homologs from other organisms hydrolyze the enamine/imine intermediates that Thr dehydratase forms from Ser or Thr. In S. enterica, the Ser-derived enamine/imine inactivates a branched-chain aminotransferase; RidA prevents this damage. Arabidopsis thaliana and maize (Zea mays) have a RidA homolog that is predicted to be plastidial. Expression of either homolog complemented the Ser sensitivity of the S. enterica ridA mutant. The purified proteins hydrolyzed the enamines/imines formed by Thr dehydratase from Ser or Thr and protected the Arabidopsis plastidial branched-chain aminotransferase BCAT3 from inactivation by the Ser-derived enamine/imine. In vitro chloroplast import assays and in vivo localization of green fluorescent protein fusions showed that Arabidopsis RidA and Thr dehydratase are chloroplast targeted. Disrupting Arabidopsis RidA reduced root growth and raised the root and shoot levels of the branched-chain amino acid biosynthesis intermediate 2-oxobutanoate; Ser treatment exacerbated these effects in roots. Supplying Ile reversed the root growth defect. These results indicate that plastidial RidA proteins can preempt damage to BCAT3 and Ile biosynthesis by hydrolyzing the Ser-derived enamine/imine product of Thr dehydratase.

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Differential Age-Dependent Import Regulation by Signal Peptides

Abstract: The import of certain proteins into chloroplasts is dependent on the age of the organelle, with age-dependent import being controlled by a specific motif within the signal peptide.

Cited by 59 publications

References 50 publications

Sequence Motifs in Transit Peptides Act as Independent Functional Units and Can Be Transferred to New Sequence Contexts

Sequence Motifs in Transit Peptides Act as Independent Functional Units and Can Be Transferred to New Sequence Contexts

Non-native, N-terminal Hsp70 Molecular Motor Recognition Elements in Transit Peptides Support Plastid Protein Translocation

Arabidopsis and Maize RidA Proteins Preempt Reactive Enamine/Imine Damage to Branched-Chain Amino Acid Biosynthesis in Plastids

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