Related Experiment Video
Updated: Jul 13, 2026
06:29
Studying Protein Import into Chloroplasts Using Protoplasts
Published on: December 10, 2018
Transport of nuclear-encoded proteins into secondarily evolved plastids
Franziska Hempel1, Andrew Bozarth, Maik S Sommer
1Laboratory for Cell Biology, Philipps-University of Marburg, Karl-von-Frisch Strasse 8, D-35032 Marburg, Germany.
Biological Chemistry
|August 19, 2007
Summary
Secondary plastids in algae evolved through engulfment. This review explores cellular mechanisms for protein transport across multiple membranes into these complex organelles.
Area of Science:
- * Cell Biology
- * Evolutionary Biology
- * Biochemistry
Background:
- * Secondary plastids in algae originated from the engulfment of eukaryotic phototrophs by heterotrophic cells.
- * These plastids are characterized by three or four surrounding membranes.
- * Most genes for plastid functions are now located in the host cell nucleus.
Purpose of the Study:
- * To review current models and findings on protein transport into secondary plastids.
- * To explain the cellular mechanisms underlying this complex process.
Main Methods:
- * Literature review of recent research on protein targeting and transport.
- * Analysis of cellular models explaining protein translocation across multiple membranes.
Main Results:
- * Proteins destined for secondary plastids must traverse multiple (three to five) membranes.
- * Recent findings shed light on the sophisticated cellular machinery involved.
Conclusions:
- * Understanding protein transport is crucial for comprehending the biology of secondary plastids.
- * Ongoing research continues to unravel the complexities of organelle biogenesis and protein targeting.
Related Concept Videos
01:18Protein 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...
01:11Protein 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.
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.
02:19Export of Mitochondrial and Chloroplast Genes
A eukaryotic cell can have up to three different types of genetic systems: nuclear, mitochondrial, and chloroplast. During evolution, organelles have exported many genes to the nucleus; this transfer is still ongoing in some plant species. Approximately 18% of the Arabidopsis thaliana nuclear genome is thought to be derived from the chloroplast’s cyanobacterial ancestor, and around 75% of the yeast genome derived from the mitochondria’s bacterial ancestor. This export has occurred irrespective...
01:45Overview of Protein Sorting and Transport
Eukaryotic cells have different membrane-bound organelles with distinct protein requirements. The process by which proteins are targeted to a specific organelle is called protein sorting.
Protein sorting can be of two types: signal-based sorting and vesicle-based trafficking. In signal-based sorting, specific amino acid sequences called sorting signals target proteins to the proper location inside the cell either via gated transport or by protein translocation. In gated transport, folded...
Protein sorting can be of two types: signal-based sorting and vesicle-based trafficking. In signal-based sorting, specific amino acid sequences called sorting signals target proteins to the proper location inside the cell either via gated transport or by protein translocation. In gated transport, folded...
01:22Protein Transport to the Thylakoids
Thylakoids are membrane-bound sac-like structures within the chloroplast that serve as sites for photosynthesis. Thylakoid lumen contains many electron transport proteins and is enclosed by a thylakoid membrane rich in the light-harvesting complex. Proteins targeted to the thylakoids are transported as precursors and are sorted by the general TOC/TIC import pathway. Once the precursor reaches the stroma, stromal processing peptidases remove their transit signal and expose thylakoid signal...
01:24Protein 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...
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...