title: Lipid interacting regions in phosphate stress glycosyltransferase atDGD2 from Arabidopsis thaliana.
abstract: Membrane lipid glycosyltransferases (GTs) in plants are enzymes that regulate the levels of the non-bilayer prone monogalactosyldiacylglycerol (GalDAG) and the bilayer-forming digalactosyldiacylglycerol (GalGalDAG). The relative amounts of these lipids affect membrane properties such as curvature and lateral stress. During phosphate shortage, phosphate is rescued by replacing phospholipids with GalGalDAG. The glycolsyltransferase enzyme in Arabidopsis thaliana responsible for this, atDGD2, senses the bilayer properties and interacts with the membrane in a monotopic manner. To understand the parameters that govern this interaction, we have identified several possible lipid-interacting sites in the protein and studied these by biophysical techniques. We have developed a multivariate discrimination algorithm that correctly predicts the regions in the protein that interact with lipids, and the interactions were confirmed by a variety of biophysical techniques. We show by bioinformatic methods and circular dichroism (CD), fluorescence, and NMR spectroscopic techniques that two regions are prone to interact with lipids in a surface-charge dependent way. Both of these regions contain Trp residues, but here charge appears to be the dominating feature governing the interaction. The sequence corresponding to residues 227-245 in the protein is seen to be able to adapt its structure according to the surface-charge density of a bilayer. All results indicate that this region interacts specifically with lipid molecules and that a second region in the protein, corresponding to residues 130-148, also interacts with the bilayer. On the basis of this, and sequence charge features in the immediate environment of S227-245, a response model for the interaction of atDGD2 with the membrane bilayer interface is proposed.
authors.affiliation: Department of Biochemistry and Biophysics, Center for Biomembrane Research, The Arrhenius Laboratory, Stockholm University, Stockholm, Sweden.
authors.forename: Scarlett
authors.initials: S
authors.lastname: Szpryngiel
authors.forename: Changrong
authors.initials: C
authors.lastname: Ge
authors.forename: Irina
authors.initials: I
authors.lastname: Iakovleva
authors.forename: Alexander
authors.initials: A
authors.lastname: Georgiev
authors.forename: Jesper
authors.initials: J
authors.lastname: Lind
authors.forename: Ake
authors.initials: A
authors.lastname: Wieslander
authors.forename: Lena
authors.initials: L
authors.lastname: Mäler
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D002942:Circular Dichroism; D016695:Glycosyltransferases / Q000737:chemistry / Q000378:metabolism*; D050356:Lipid Metabolism; D008969:Molecular Sequence Data; D015999:Multivariate Analysis; D019906:Nuclear Magnetic Resonance, Biomolecular; D010710:Phosphates / Q000378:metabolism*; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D013050:Spectrometry, Fluorescence
chemical_list: D029681:Arabidopsis Proteins; D010710:Phosphates; D016695:Glycosyltransferases