NMR structure and conformational dynamics of AtPDFL2.1, a defensin-like peptide from Arabidopsis thaliana.
Plant defensins constitute the innate immune response against pathogens such as fungi and bacteria. Typical plant defensins are small, basic peptides that possess a characteristic three-dimensional fold stabilized by three or four disulfide bridges. In addition to known defensin genes, the Arabidopsis genome comprises >300 defensin-like genes coding for small cysteine-rich peptides. One of such genes encodes for AtPDFL2.1, a putative antifungal peptide of 55 amino acids, with six cysteine residues in its primary sequence. To understand the functional role of AtPDFL2.1, we carried out antifungal activity assays and determined its high-resolution three-dimensional structure using multidimensional solution NMR spectroscopy. We found that AtPDFL2.1 displays a strong inhibitory effect against Fusarium graminearum (IC50≈4μM). This peptide folds in the canonical cysteine-stabilized αβ (CSαβ) motif, consisting of one α-helix and one triple-stranded antiparallel β-sheet stabilized by three disulfide bridges and a hydrophobic cluster of residues within its core where the α-helix packs tightly against the β-sheets. Nuclear spin relaxation measurements show that the structure of AtPDFL2.1 is essentially rigid, with the L3 loop located between β-strands 2 and 3 being more flexible and displaying conformational exchange. Interestingly, the dynamic features of loop L3 are conserved among defensins and are probably correlated to the antifungal and receptor binding activities.
Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, United States; Department of Crop Sciences, Division of Plant Protection, University of Natural Resources and Life Sciences, Vienna, Austria.
Reza
R
Omidvar
Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, United States.
Youlin
Y
Xia
Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, United States; DIBAF - University of Tuscia - Largo dell'Universita', Blocco D, 01100, Viterbo, Italy.
Fernando
F
Porcelli
Department of Crop Sciences, Division of Plant Protection, University of Natural Resources and Life Sciences, Vienna, Austria.
Holger
H
Bohlmann
Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, United States; Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, United States. Electronic address: vegli001@umn.edu.
Gianluigi
G
Veglia
D000595:Amino Acid Sequence; D000935:Antifungal Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D017124:Conserved Sequence; D023082:Defensins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005670:Fusarium / Q000187:drug effects; D017343:Genes, Plant; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D055550:Protein Stability; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity
D000935:Antifungal Agents; D029681:Arabidopsis Proteins; D023082:Defensins
Antifungal activity; AtPDFL2.1; Conformational dynamics; Plant defensins; Solution NMR; Three-dimensional structure