The thylakoid membrane protein ALB3 associates with the cpSecY-translocase in Arabidopsis thaliana.

The integration of light-harvesting chlorophyll proteins (LHCPs) into the thylakoid membrane requires the integral thylakoid membrane protein ALB3, a homologue of the bacterial cytoplasmic membrane protein YidC. In bacteria, YidC is associated with the SecY-translocase and facilitates the integration of Sec-dependent proteins into the plasma membrane. In addition, it is ...
also involved in the insertion of Sec-independent proteins. In the present study we demonstrate, in Arabidopsis thaliana, that most ALB3 is a constituent of an oligomeric complex of approx. 180 kDa. In addition, we detected ALB3 in several higher-molecular-mass complexes (up to 700 kDa). Furthermore, we show that most ALB3 co-fractionates with cpSecY during gel-filtration analysis and blue native gel electrophoresis, suggesting an association of ALB3 with the cpSecY complex. A direct interaction of ALB3 with the cpSecY complex was demonstrated by co-immunoprecipitation experiments using digitonin-solubilized thylakoid membrane proteins and anti-cpSecY or anti-ALB3 antibodies. This result was further confirmed by electron microscopic co-immunolocalization of ALB3 and cpSecY. In addition, an association of ALB3 with the cpSecY complex was demonstrated directly by cross-linking experiments using the chemical cross-linker disuccinimidyl suberate.
Mesh Terms:
Arabidopsis, Arabidopsis Proteins, Chloroplasts, Chromatography, Gel, Cross-Linking Reagents, DNA, Complementary, Electrophoresis, Polyacrylamide Gel, Immunohistochemistry, Light-Harvesting Protein Complexes, Membrane Proteins, Microscopy, Electron, Photosynthetic Reaction Center Complex Proteins, Precipitin Tests, Protein Binding, Protein Transport, Thylakoids
Biochem. J.
Date: Dec. 15, 2002
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