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Tryptophan residues promote membrane association for a plant lipid glycosyltransferase involved in phosphate stress
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Ge, C. R., Georgiev, A., Ohman, A., Wieslander, A. and Kelly, A. A.. (2011) Tryptophan residues promote membrane association for a plant lipid glycosyltransferase involved in phosphate stress. Journal of Biological Chemistry, Vol.286 (No.8). pp. 6669-6684. ISSN 0021-9258
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Official URL: http://dx.doi.org/10.1074/jbc.M110.138495
Abstract
Chloroplast membranes contain a substantial excess of the nonbilayer-prone monogalactosyldiacylglycerol (GalDAG) over the biosynthetically consecutive, bilayer-forming digalactosyldiacylglycerol (GalGalDAG), yielding a high membrane curvature stress. During phosphate shortage, plants replace phospholipids with GalGalDAG to rescue phosphate while maintaining membrane homeostasis. Here we investigate how the activity of the corresponding glycosyltransferase (GT) in Arabidopsis thaliana (atDGD2) depends on local bilayer properties by analyzing structural and activity features of recombinant protein. Fold recognition and sequence analyses revealed a two-domain GT-B monotopic structure, present in other plant and bacterial glycolipid GTs, such as the major chloroplast GalGalDAG GT atDGD1. Modeling led to the identification of catalytically important residues in the active site of atDGD2 by site-directed mutagenesis. The DGD synthases share unique bilayer interface segments containing conserved tryptophan residues that are crucial for activity and for membrane association. More detailed localization studies and liposome binding analyses indicate differentiated anchor and substrate-binding functions for these separated enzyme interface regions. Anionic phospholipids, but not curvature-increasing nonbilayer lipids, strongly stimulate enzyme activity. From our studies, we propose a model for bilayer "control" of enzyme activity, where two tryptophan segments act as interface anchor points to keep the substrate region close to the membrane surface. Binding of the acceptor substrate is achieved by interaction of positive charges in a surface cluster of lysines, arginines, and histidines with the surrounding anionic phospholipids. The diminishing phospholipid fraction during phosphate shortage stress will then set the new GalGalDAG/phospholipid balance by decreasing stimulation of atDGD2.
| Item Type: | Journal Article |
|---|---|
| Divisions: | Faculty of Science > Life Sciences (2010- ) > Warwick HRI (2004-2010) |
| Journal or Publication Title: | Journal of Biological Chemistry |
| Publisher: | American Society for Biochemistry and Molecular Biology |
| ISSN: | 0021-9258 |
| Date: | 25 February 2011 |
| Volume: | Vol.286 |
| Number: | No.8 |
| Page Range: | pp. 6669-6684 |
| Identification Number: | 10.1074/jbc.M110.138495 |
| Status: | Peer Reviewed |
| Publication Status: | Published |
| Access rights to Published version: | Restricted or Subscription Access |
| Funder: | Wenner-Gren Foundation , Royal Swedish Academy of Sciences, European Commission (EC), Swedish Research Council |
| URI: | http://wrap.warwick.ac.uk/id/eprint/41581 |
Data sourced from Thomson Reuters' Web of Knowledge
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