GREEN FLUORESCENT PROTEIN variants with enhanced folding are more efficiently imported into chloroplasts
Jinseung Jeong1, Byeongho Moon2, Inhwan Hwang2
1Department of Integrative Food, Bioscience and Biotechnology, Chonnam National University, Gwangju 61186, South Korea.
Plant Physiology
|June 14, 2022
Summary
Chloroplast and mitochondrial protein import differs; chloroplasts tolerate varied protein folding, while mitochondria require unfolded proteins for efficient import into these organelles.
Area of Science:
- Cell Biology
- Organelle Biogenesis
Background:
- Chloroplasts and mitochondria, originating from bacteria, possess their own genomes but rely on nuclear-encoded proteins.
- Protein import into these organelles typically requires unfolding, but the precise role of protein folding properties remains unclear.
Purpose of the Study:
- To investigate how protein folding affects import into chloroplasts and mitochondria.
- To compare the import behavior of normal green fluorescent protein (GFP) with variants exhibiting enhanced folding (superfolder GFP and extra-superfolder GFP).
Main Methods:
- Utilized normal GFP, superfolder GFP (sfGFP), and extra-superfolder GFP (esGFP) as reporters for organelle import studies.
- Examined import efficiency in wild-type and mutant Arabidopsis thaliana lines affecting chloroplast import machinery (ppi2, hsp93-V) and mitochondrial import.
Main Results:
- sfGFP and esGFP showed reduced dependence on transit peptide motifs and import machinery for chloroplast import compared to normal GFP.
- Enhanced folding GFP variants were imported into chloroplasts even with a mutated transit peptide, unlike normal GFP.
- Mitochondrial import of sfGFP and esGFP was significantly impaired, suggesting a requirement for unfolded proteins.
Conclusions:
- Chloroplast import machinery demonstrates greater tolerance to diverse preprotein folding states.
- Mitochondrial import machinery is more specialized, preferentially translocating unfolded preproteins.
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