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PMID:17938172

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Citation

Lu, B, Xu, C, Awai, K, Jones, AD and Benning, C (2007) A small ATPase protein of Arabidopsis, TGD3, involved in chloroplast lipid import. J. Biol. Chem. 282:35945-53

Abstract

Polar lipid trafficking is essential in eukaryotic cells as membranes of lipid assembly are often distinct from final destination membranes. A striking example is the biogenesis of the photosynthetic membranes (thylakoids) in plastids of plants. Lipid biosynthetic enzymes at the endoplasmic reticulum and the inner and outer plastid envelope membranes are involved. This compartmentalization requires extensive lipid trafficking. Mutants of Arabidopsis are available that are disrupted in the incorporation of endoplasmic reticulum-derived lipid precursors into thylakoid lipids. Two proteins affected in two of these mutants, trigalactosyldiacylglycerol 1 (TGD1) and TGD2, encode the permease and substrate binding component, respectively, of a proposed lipid translocator at the inner chloroplast envelope membrane. Here we describe a third protein of Arabidopsis, TGD3, a small ATPase proposed to be part of this translocator. As in the tgd1 and tgd2 mutants, triacylglycerols and trigalactolipids accumulate in a tgd3 mutant carrying a T-DNA insertion just 5' of the TGD3 coding region. The TGD3 protein shows basal ATPase activity and is localized inside the chloroplast beyond the inner chloroplast envelope membrane. Proteins orthologous to TGD1, -2, and -3 are predicted to be present in Gram- bacteria, and the respective genes are organized in operons suggesting a common biochemical role for the gene products. Based on the current analysis, it is hypothesized that TGD3 is the missing ATPase component of a lipid transporter involving TGD1 and TGD2 required for the biosynthesis of ER-derived thylakoid lipids in Arabidopsis.

Links

PubMed Online version:10.1074/jbc.M704063200

Keywords

Adenosine Triphosphatases/genetics; Adenosine Triphosphatases/metabolism; Antigens, Plant/genetics; Antigens, Plant/metabolism; Arabidopsis/enzymology; Arabidopsis/genetics; Arabidopsis Proteins/genetics; Arabidopsis Proteins/metabolism; Biological Transport/physiology; Carrier Proteins/genetics; Carrier Proteins/metabolism; Endoplasmic Reticulum/genetics; Endoplasmic Reticulum/metabolism; Gram-Negative Bacteria/enzymology; Gram-Negative Bacteria/genetics; Intracellular Membranes/enzymology; Lipid Metabolism/physiology; Lipids; Membrane Transport Proteins/genetics; Membrane Transport Proteins/metabolism; Operon/physiology; Plant Proteins/genetics; Plant Proteins/metabolism; Thylakoids/enzymology; Thylakoids/genetics

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

ARATH:TGD3

located_in

GO:0009507: chloroplast

ECO:0000314: direct assay evidence used in manual assertion

C

Seeded From UniProt

complete

ARATH:TGD3

acts_upstream_of_or_within

GO:0006869: lipid transport

ECO:0000315: mutant phenotype evidence used in manual assertion

P

Seeded From UniProt

complete

ARATH:TGD3

enables

GO:0016887: ATP hydrolysis activity

ECO:0000314: direct assay evidence used in manual assertion

F

Seeded From UniProt

complete


See also

References

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