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Related Concept Videos

The Anatomy of Chloroplasts01:08

The Anatomy of Chloroplasts

Green algae and plants, including green stems and unripe fruit, harbor specialized organelles called chloroplasts to carry out photosynthesis. They coordinate both stages of photosynthesis — the light-dependent reactions and the light-independent reactions. The light-dependent reactions use sunlight to release oxygen and produce chemical energy in the form of ATP and NADPH, and the light-independent reactions capture CO2 and use ATP and NADPH to produce sugar.
Structure of Chloroplasts
A...
Anatomy of Chloroplasts01:07

Anatomy of Chloroplasts

Green algae and plants, including green stems and unripe fruit, harbor chloroplasts—the vital organelles where photosynthesis takes place. In plants, the highest density of chloroplasts is found in the mesophyll cells of leaves.
Protein Transport to the Outer Chloroplast Membrane01:11

Protein Transport to the Outer Chloroplast Membrane

Chloroplast outer membrane proteins encoded by the nucleus are synthesized in the cytosol. Soon after synthesis, they bind cytosolic factors such as 14-3-3 protein and the Hsp70 chaperones that keep these precursors in an unfolded state until their translocation.
Two models describe the mechanism of precursor recognition and entry across the outer membrane through the TOC complex. Model 1 suggests the newly synthesized precursor binds to the TOC receptor 159 and forms a complex.
Protein Transport to the Inner Chloroplast Membrane01:18

Protein Transport to the Inner Chloroplast Membrane

Proteins targeted to the inner chloroplast membrane, or plastid proteins, are transported by two general pathways: the stop-transfer and the re-insertion or post-import pathways. Most plastid proteins carry N-terminal transit sequences and internal import sequences targeting it to the specific chloroplast subcompartment. Proteins targeted by the stop-transfer pathway have internal hydrophobic sequences that inhibit their translocation into the stroma. As a result, these precursors are arrested...
Protein Transport to the Stroma01:24

Protein Transport to the Stroma

Chloroplasts are triple membrane structures with an outer membrane, an inner membrane, and a thylakoid membrane, each containing distinct metabolite transporters, membrane translocons, and enzymes. Appropriate sorting and translocating these proteins to their correct membrane systems is essential for chloroplast function.
Protein complexes called the translocon of the outer chloroplast membrane or TOC complex, and the translocon of the inner chloroplast membrane or TIC complex mediate the...
Comparing Mitochondrial, Chloroplast, and Prokaryotic Genomes02:16

Comparing Mitochondrial, Chloroplast, and Prokaryotic Genomes

The present-day mitochondrial and chloroplast genomes have retained some of the characteristics of their ancestral prokaryotes and also have acquired new attributes during their evolution within eukaryotic cells. Like prokaryotic genomes, mitochondrial and chloroplast genomes neither bind with histone-like proteins nor show complex packaging into chromosome-like structures, as observed in eukaryotes. Unlike mitotic cell divisions observed in eukaryotic cells, mitochondria and chloroplasts...

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Related Experiment Video

Updated: May 9, 2026

Preparation of Chloroplast Sub-compartments from Arabidopsis for the Analysis of Protein Localization by Immunoblotting or Proteomics
10:28

Preparation of Chloroplast Sub-compartments from Arabidopsis for the Analysis of Protein Localization by Immunoblotting or Proteomics

Published on: October 19, 2018

Evolution of chloroplast J proteins.

Chi-Chou Chiu1, Lih-Jen Chen, Pai-Hsiang Su

  • 1Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan.

Plos One
|July 30, 2013
PubMed
Summary

Arabidopsis chloroplasts possess at least 19 J proteins, expanding cochaperone diversity in land plants. These J proteins, with novel motifs, likely mediate tissue-specific biosynthesis functions for heat shock protein 70 (Hsp70) chaperones.

Area of Science:

  • Plant Biology
  • Molecular Biology
  • Evolutionary Biology

Background:

  • Heat shock protein 70 (Hsp70) chaperones are crucial for cellular processes.
  • J proteins act as cochaperones, directing Hsp70s to specific functions.
  • Understanding chloroplast J proteins is key to plant cell biology and evolution.

Purpose of the Study:

  • To identify and characterize the J protein complement in Arabidopsis chloroplasts.
  • To investigate the evolutionary expansion of J proteins in land plants.
  • To explore the functional implications of novel J proteins in chloroplasts.

Main Methods:

  • Genomic and proteomic database searches for J proteins in Arabidopsis.
  • Individual protein import assays to confirm chloroplast localization.

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A New Approach for the Comparative Analysis of Multiprotein Complexes Based on 15N Metabolic Labeling and Quantitative Mass Spectrometry
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A New Approach for the Comparative Analysis of Multiprotein Complexes Based on 15N Metabolic Labeling and Quantitative Mass Spectrometry

Published on: March 13, 2014

Analysis of Protein Import into Chloroplasts Isolated from Stressed Plants
10:18

Analysis of Protein Import into Chloroplasts Isolated from Stressed Plants

Published on: November 1, 2016

Related Experiment Videos

Last Updated: May 9, 2026

Preparation of Chloroplast Sub-compartments from Arabidopsis for the Analysis of Protein Localization by Immunoblotting or Proteomics
10:28

Preparation of Chloroplast Sub-compartments from Arabidopsis for the Analysis of Protein Localization by Immunoblotting or Proteomics

Published on: October 19, 2018

A New Approach for the Comparative Analysis of Multiprotein Complexes Based on 15N Metabolic Labeling and Quantitative Mass Spectrometry
08:04

A New Approach for the Comparative Analysis of Multiprotein Complexes Based on 15N Metabolic Labeling and Quantitative Mass Spectrometry

Published on: March 13, 2014

Analysis of Protein Import into Chloroplasts Isolated from Stressed Plants
10:18

Analysis of Protein Import into Chloroplasts Isolated from Stressed Plants

Published on: November 1, 2016

  • Phylogenetic analysis to classify J proteins into clades.
  • Gene expression analysis under various conditions.

    • Main Results:

    • Arabidopsis chloroplasts contain at least 19 J proteins, the highest number reported for any organelle.
    • These J proteins fall into 11 distinct clades, with 7 clades unique to land plants.
    • Land plant-specific J proteins possess novel motifs and exhibit tissue-specific expression patterns.
    • Expression of new J proteins is often downregulated by low temperatures.

    Conclusions:

    • Chloroplast J protein diversity significantly increased during land plant evolution.
    • The expansion involved acquiring new J proteins with unique motifs, not gene duplication within families.
    • These novel J proteins likely confer specialized, tissue-specific roles in biosynthesis rather than stress response for Hsp70 chaperones.