The structure of "defective in induced resistance" protein of Arabidopsis thaliana, DIR1, reveals a new type of lipid transfer protein.
Screening of transfer DNA (tDNA) tagged lines of Arabidopsis thaliana for mutants defective in systemic acquired resistance led to the characterization of dir1-1 (defective in induced resistance [systemic acquired resistance, SAR]) mutant. It has been suggested that the protein encoded by the dir1 gene, i.e., DIR1, is involved in the long distance signaling associated with SAR. DIR1 displays the cysteine signature of lipid transfer proteins, suggesting that the systemic signal could be lipid molecules. However, previous studies have shown that this signature is not sufficient to define a lipid transfer protein, i.e., a protein capable of binding lipids. In this context, the lipid binding properties and the structure of a DIR1-lipid complex were both determined by fluorescence and X-ray diffraction. DIR1 is able to bind with high affinity two monoacylated phospholipids (dissociation constant in the nanomolar range), mainly lysophosphatidyl cholines, side-by-side in a large internal tunnel. Although DIR1 shares some structural and lipid binding properties with plant LTP2, it displays some specific features that define DIR1 as a new type of plant lipid transfer protein. The signaling function associated with DIR1 may be related to a specific lipid transport that needs to be characterized and to an additional mechanism of recognition by a putative receptor, as the structure displays on the surface the characteristic PxxP structural motif reminiscent of SH3 domain signaling pathways.
Université Paris Descartes, CNRS, Laboratoire de Cristallographie et RMN Biologiques (UMR 8015), Paris 75006, France.
Marie-Bernard
MB
Lascombe
Bénédicte
B
Bakan
Nathalie
N
Buhot
Didier
D
Marion
Jean-Pierre
JP
Blein
Valéry
V
Larue
Chris
C
Lamb
Thierry
T
Prangé
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D052179:Antigens, Plant / Q000737:chemistry* / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D016384:Consensus Sequence; D003545:Cysteine / Q000737:chemistry; D004220:Disulfides / Q000737:chemistry; D050556:Fatty Acid-Binding Proteins; D057927:Hydrophobic and Hydrophilic Interactions; D007526:Isoelectric Point; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009154:Mutation; D010455:Peptides / Q000737:chemistry; D010743:Phospholipids / Q000378:metabolism; D010802:Phylogeny; D010843:Pichia / Q000235:genetics; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D015398:Signal Transduction / Q000235:genetics; D015032:Zinc / Q000737:chemistry
D052179:Antigens, Plant; D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D004220:Disulfides; D050556:Fatty Acid-Binding Proteins; D010455:Peptides; D010743:Phospholipids; D010940:Plant Proteins; C466483:dir1-1 protein, Arabidopsis; C511920:lipid transfer proteins, plant; C011083:polyproline; D015032:Zinc; D003545:Cysteine