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The Ins and Outs of Chloroplast Protein Transport

  • Qihua Ling
  • Raphael Trösch
  • Paul JarvisEmail author
Chapter
Part of the Advances in Photosynthesis and Respiration book series (AIPH, volume 36)

Summary

Much of the chloroplast proteome is encoded in the nuclear genome and needs to be imported post-translationally. Information for the organellar targeting of these imported proteins lies in an N-terminal leader sequence, the transit peptide, which is specifically bound by receptor components at the chloroplast surface. These receptor components are part of the TOC (translocon at the outer envelope membrane of chloroplasts) complex, which, together with the TIC (translocon at the inner envelope membrane of chloroplasts) machinery, mediates the translocation of precursor proteins into chloroplasts. Apart from the receptors, these complexes incorporate channel, motor and regulatory functions. Many components of this TOC/TIC apparatus have been identified. Multiple isoforms of the TOC receptors (and possibly of some other components) enable the operation of different import pathways with different substrate preferences, perhaps so that non-abundant proteins can be imported without serious competition from highly-abundant proteins of the photosynthetic apparatus. The different import pathways might also play a role in the differentiation of different plastid types. While much research has focused on these canonical TOC/TIC-mediated import routes, a number of studies have revealed alternative protein transport pathways to chloroplasts that employ different mechanisms; one of these passes through the endoplasmic reticulum and the Golgi apparatus. Other recent studies have revealed several protein targeting pathways leading to the envelope itself.

Keywords

Protein Import Transit Peptide Intermembrane Space Chloroplast Protein Envelope Membrane 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Abbreviations:

aaRS

Aminoacyl-tRNA synthetase;

AKR2A

Ankyrin repeat-containing protein 2A;

APG1

Albino or pale green mutant 1;

BamA

β-barrel assembly machinery A;

CAH1

Carbonic anhydrase 1;

ceQORH

Chloroplast envelope quinone oxidoreductase homologue;

CIA2 (-5)

Chloroplast import apparatus 2 (-5);

ClpC

Caseinolytic protease, subunit C;

Com44/Cim44

Chloroplast outer/inner membrane proteins, 44 kD;

Cpn60

Chaperonin, 60 kD;

DEPC

Diethylpyrocarbonate;

Fd

Ferredoxin;

FNR

Ferredoxin-NADP+ reductase;

GAP

GTPase activating protein;

GEF

Guanine nucleotide exchange factor;

Hip

Hsp70-interacting protein;

Hop

Hsp70/Hsp90-organizing protein;

Hsp70 (-93, -100)

Heat-shock protein, 70 kD (93 kD, 100 kD);

IDP

Intrinsically disordered protein;

LHCII

Light-harvesting complex protein of photosystem II;

MGD1

Monogalactosyldiacylglycerol synthase 1;

OEP

Outer envelope protein, kD;

PAGE

Polyacrylamide gel electrophoresis;

PIC1

Permease in chloroplasts 1;

POTRA

Polypeptide transport associated;

ppi1 (-2, -3)

– Plastid protein import 1 (-2, -3);

PreP

Presequence protease;

SAM (Sam)

Sorting and assembly machinery;

SP1 (sp1)

Suppressor of ppi1 locus 1;

SRP

Signal recognition particle;

SSU (pSSU)

Rubisco small subunit (precursor of);

Sti1

Stress-inducible 1;

Tat

Twin-arginine translocase;

TIC (Tic)

Translocon at the inner envelope membrane of chloroplasts;

TIM (Tim)

Translocase of the inner mitochondrial membrane;

TOC (Toc)

Translocon at the outer envelope membrane of chloroplasts;

TOM (Tom)

Translocase of the outer mitochondrial membrane;

TPP

Thylakoidal processing peptidase;

TPR

Tetratricopeptide repeat;

TROL

Thylakoid rhodanese-like protein;

VIPP1

Vesicle-inducing protein in plastids 1

Notes

Acknowledgments

The authors acknowledge the support of a Gatsby Charitable Foundation Sainsbury PhD Studentship (to RT), and of Biotechnology and Biological Sciences Research Council (BBSRC) grants BB/D016541/1 and BB/H008039/1 (to QL and PJ).

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© Springer Science+Business Media Dordrecht 2013

Authors and Affiliations

  1. 1.Department of Biology, Adrian BuildingUniversity of LeicesterLeicesterUK

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