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. 180kDa. In addition, we detected ALB3 in several higher-molecular-mass complexes (up to 700kDa). 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.
The thylakoid membrane protein ALB3 associates with the cpSecY-translocase in Arabidopsis thaliana
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Eva KLOSTERMANN, Imke DROSTE gen. HELLING, Jean-Pierre CARDE, Danja SCHÜNEMANN; The thylakoid membrane protein ALB3 associates with the cpSecY-translocase in Arabidopsis thaliana. Biochem J 15 December 2002; 368 (3): 777–781. doi: https://doi.org/10.1042/bj20021291
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