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

Biochem J. 2002 Dec 15;368(Pt 3):777-81. doi: 10.1042/BJ20021291.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / chemistry*
  • Arabidopsis Proteins / metabolism*
  • Chloroplast Proteins
  • Chloroplasts / metabolism
  • Chromatography, Gel
  • Cross-Linking Reagents / pharmacology
  • DNA, Complementary / metabolism
  • Electrophoresis, Polyacrylamide Gel
  • Immunohistochemistry
  • Light-Harvesting Protein Complexes
  • Membrane Proteins / metabolism*
  • Microscopy, Electron
  • Photosynthetic Reaction Center Complex Proteins / metabolism*
  • Precipitin Tests
  • Protein Binding
  • Protein Transport
  • SEC Translocation Channels
  • Thylakoids / metabolism*


  • ALBINO 3 protein, Arabidopsis
  • Arabidopsis Proteins
  • Chloroplast Proteins
  • Cross-Linking Reagents
  • DNA, Complementary
  • Light-Harvesting Protein Complexes
  • Membrane Proteins
  • Photosynthetic Reaction Center Complex Proteins
  • SCY1 protein, Arabidopsis
  • SEC Translocation Channels