Poster: Membrane transport

Abs # 170: A multipartite ABC transporter in the chloroplast envelopes involved in lipid trafficking in Arabidopsis

Presenter:	Xu, Changcheng , xuch@msu.edu
Authors	Xu, Changcheng  (A)   Awai, Koichiro  (A)   Benning, Christoph  (A)
Affiliations:	(A): Department of Biochemistry and Molecular Biology, Michigan State University, MI 48824

Membrane lipid transfer between subcellular membranes is essential for the growth and maintenance of eukaryotic and bacterial cells. The isolation of genetic mutants of the model plant Arabidopsis with deficiencies in the transfer of polar lipids from the endoplasmic reticulum (ER) to the photosynthetic membranes in chloroplasts has provided exciting new opportunities to gain mechanistic insights into lipid transfer processes in eukaryotic and bacterial cells. Positional cloning of two mutant loci and disruption of a third predicted gene led to the identification of three Arabidopsis proteins with striking similarity to the permease-, substrate-binding-, and ATP-binding proteins of predicted bacterial ABC transporters with generally unknown function, but which are widespread and possibly ubiquitous in bacteria. Based on in vivo labeling and subcellular localization data, it is proposed that the three Arabidopsis proteins are components of a phospholipid translocator in the chloroplast envelopes. Disruption of the transporter inactivates the transfer of lipid moieties from the ER to the plastid and causes the ectopic accumulation of triacylgycerols and oligogalactolipids in leaves of the three respective mutants.