Processing of the precursors for the light-harvesting chlorophyll-binding proteins of photosystem II and photosystem I during import and in an organelle-free assay

We have investigated whether the precursors for the light-harvesting chlorophyll a/b binding proteins (LHCP) of photosystems II and I (PSII and PSI) are cleavable substrates in an organelle-free reaction, and have compared the products with those obtained during in vitro import into chloroplasts. Re...

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Bibliographic Details
Published in:Plant physiology (Bethesda) 1992-02, Vol.98 (2), p.595-601
Main Authors: Clark, Steven E., Lamppa, Gayle K.
Format: Article
Language:English
Subjects:
Biological and medical sciences
Cell biochemistry
Cell physiology
Cellular and Structural Biology
chlorophylle
Chlorophylls
chloroplaste
Chloroplasts
clorofilas
cloroplasto
Enzymes
fotosintesis
Fundamental and applied biological sciences. Psychology
Genes
genetica
genetics
genetique
Imports
light
lumiere
luz
lycopersicon esculentum
Peas
photosynthese
photosynthesis
Plant physiology and development
Plants
Protein precursors
proteinas
proteine
Proteins
Wheat
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Summary:We have investigated whether the precursors for the light-harvesting chlorophyll a/b binding proteins (LHCP) of photosystems II and I (PSII and PSI) are cleavable substrates in an organelle-free reaction, and have compared the products with those obtained during in vitro import into chloroplasts. Representatives from the tomato (Lycopersicon esculentum) LHCP family were analyzed. The precursor for LHCP type I of PSII (pLHCPII-encoded 1), by the tomato gene Cab3C, was cleaved at only one site in the organelle-free assay, but two sites were recognized during import, analogous to our earlier results with a wheat precursor for LHCPII-1. The relative abundance of the two peptides produced was investigated during import of pLHCPII-1 into chloroplasts isolated from plants greened for 2 or 24 hours. In contrast to pLHCPII-1, the precursors for LHCP type II and III of PSI were cleaved in both assays, giving rise to a single peptide. The precursor for LHCP type I of PSI, encoded by gene Cab6A, yielded two peptides of 23.5 and 21.5 kilodaltons during import, whereas in the organelle-free assay only the 23.5 kilodalton peptide was found. N-terminal sequence analysis of this radiolabeled peptide has tentatively identified the site cleaved in the organelle-free assay between met40 and ser4l of the precursor.
ISSN:0032-0889
1532-2548
DOI:10.1104/pp.98.2.595