Biochemistry, Department of
Date of this Version
2016
Citation
PNAS Early Edition
Abstract
Galactolipids [monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol
(DGDG)] are the hallmark lipids of photosynthetic
membranes. The galactolipid synthases MGD1 and DGD1
catalyze consecutive galactosyltransfer reactions but localize to the
inner and outer chloroplast envelopes, respectively, necessitating
intermembrane lipid transfer. Here we show that the N-terminal
sequence of DGD1 (NDGD1) is required for galactolipid transfer
between the envelopes. Different diglycosyllipid synthases (DGD1,
DGD2, and Chloroflexus glucosyltransferase) were introduced into
the dgd1-1 mutant of Arabidopsis in fusion with N-terminal extensions
(NDGD1 and NDGD2) targeting to the outer envelope. Reconstruction
of DGDG synthesis in the outer envelope membrane was
observed only with diglycosyllipid synthase fusion proteins carrying
NDGD1, indicating that NDGD1 enables galactolipid translocation
between envelopes. NDGD1 binds to phosphatidic acid (PA) in membranes
and mediates PA-dependent membrane fusion in vitro.
These findings provide a mechanism for the sorting and selective
channeling of lipid precursors between the galactolipid pools of the
two envelope membranes.
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Comments
Copyright 2016 Kelly et al.