Solution structure of Ace-AMP1, a potent antimicrobial protein extracted from onion seeds. Structural analogies with plant nonspecific lipid transfer proteins

Biochemistry. 1998 Mar 17;37(11):3623-37. doi: 10.1021/bi9723515.


The three-dimensional solution structure of Ace-AMP1, an antifungal protein extracted from onion seeds, was determined using 1H NMR spectroscopy and molecular modeling. This cationic protein contains 93 amino acid residues and four disulfide bridges. Its structure was determined from 1260 NOE-derived distance restraints and 173 dihedral restraints derived from NOEs and 3JCaHNH coupling constants. The global fold involves four helical segments connected by three loops and a C-terminal tail without regular secondary structures, except for a 3(10)-helix turn and a beta-turn. The most striking feature is the absence of any continuous cavity running through the whole molecule as found in recently determined structures of nonspecific transfer proteins extracted from wheat and maize seeds, although their global folds are very similar. Consistent with the absence of a cavity in the core of Ace-AMP1, it was found that this protein, in contrast to ns-LTPs, does not bind fluorescently labeled phospholipids in solution. On the other hand, Ace-AMP1 is able to interact with phospholipid membranes as shown by the release of carboxyfluorescein from the lumen of artificial liposomes and by the induction of alterations in fluorescence polarization of fluorescently labeled phospholipids embedded in artificial liposomes.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Anti-Infective Agents / chemistry*
  • Anti-Infective Agents / metabolism
  • Antigens, Plant
  • Carrier Proteins / chemistry*
  • Disulfides / chemistry
  • Molecular Sequence Data
  • Nuclear Magnetic Resonance, Biomolecular
  • Onions
  • Phospholipids / metabolism
  • Plant Proteins / chemistry*
  • Plant Proteins / metabolism
  • Protein Conformation
  • Protein Folding
  • Protein Structure, Secondary
  • Seeds / chemistry
  • Sequence Homology, Amino Acid*
  • Solutions


  • AMP1 protein, Allium cepa
  • Anti-Infective Agents
  • Antigens, Plant
  • Carrier Proteins
  • Disulfides
  • Phospholipids
  • Plant Proteins
  • Solutions
  • lipid transfer proteins, plant