Skip to main content
padlock icon - secure page this page is secure

Free Content TGD4 involved in endoplasmic reticulum‐to‐chloroplast lipid trafficking is a phosphatidic acid binding protein

Download Article:

The synthesis of galactoglycerolipids, which are prevalent in photosynthetic membranes, involves enzymes at the endoplasmic reticulum (ER) and the chloroplast envelope membranes. Genetic analysis of trigalactosyldiacylglycerol (TGD) proteins in Arabidopsis has demonstrated their role in polar lipid transfer from the ER to the chloroplast. The TGD1, 2, and 3 proteins resemble components of a bacterial‐type ATP‐binding cassette (ABC) transporter, with TGD1 representing the permease, TGD2 the substrate binding protein, and TGD3 the ATPase. However, the function of the TGD4 protein in this process is less clear and its location in plant cells remains to be firmly determined. The predicted C‐terminal β‐barrel structure of TGD4 is weakly similar to proteins of the outer cell membrane of Gram‐negative bacteria. Here, we show that, like TGD2, the TGD4 protein when fused to DsRED specifically binds phosphatidic acid (PtdOH). As previously shown for tgd1 mutants, tgd4 mutants have elevated PtdOH content, probably in extraplastidic membranes. Using highly purified and specific antibodies to probe different cell fractions, we demonstrated that the TGD4 protein was present in the outer envelope membrane of chloroplasts, where it appeared to be deeply buried within the membrane except for the N‐terminus, which was found to be exposed to the cytosol. It is proposed that TGD4 is either directly involved in the transfer of polar lipids, possibly PtdOH, from the ER to the outer chloroplast envelope membrane or in the transfer of PtdOH through the outer envelope membrane.
No References
No Citations
No Supplementary Data
No Article Media
No Metrics

Document Type: Research Article

Affiliations: 1: Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA 2: Brookhaven National Laboratory, Biology Department, Upton, NY 11973-5000, USA

Publication date: May 1, 2012

  • Access Key
  • Free content
  • Partial Free content
  • New content
  • Open access content
  • Partial Open access content
  • Subscribed content
  • Partial Subscribed content
  • Free trial content
Cookie Policy
Cookie Policy
Ingenta Connect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more