H NMR study of the solution structure of Ac-AMP2, a sugar binding antimicrobial protein isolated from Amaranthus caudatus.

TitleH NMR study of the solution structure of Ac-AMP2, a sugar binding antimicrobial protein isolated from Amaranthus caudatus.
Publication TypeJournal Article
Year of Publication1996
AuthorsMartins, J. C., D. Maes, R. Loris, H. A. Pepermans, L. Wyns, R. Willem, and P. Verheyden
JournalJ Mol Biol
Volume258
Issue2
Pagination322-33
Date Published1996 May 3
ISSN0022-2836
KeywordsAmino Acid Sequence, Antifungal Agents, Base Sequence, Carbohydrates, Disulfides, Magnetic Resonance Spectroscopy, Models, Molecular, Molecular Sequence Data, Plant Proteins, Plants, Protein Conformation, Protein Structure, Secondary, Seeds, Sequence Homology, Amino Acid, Solutions
Abstract

The conformation in water of antimicrobial protein 2 from Amaranthus caudatus (Ac-AMP2) was determined using 1H NMR, DIANA and restrained molecular modeling. Ac-AMP2 is a 30 amino acid residue, lectin-like protein that specifically binds to chitin, a polymer of beta-1,4-N-acetyl-D-glucosamine. After sequence specific resonance assignments, a total of 198 distance restraints were collected from 2D NOESY buildup spectra at 500 MHz at pH 2, supplemented by a 2D NOESY spectrum at 600 MHz. The location of the three previously unassigned disulfide bridges was determined from preliminary DIANA structures, using a statistical analysis of intercystinyl distances. The solution structure of Ac-AMP2 is presented as a set of 26 DIANA structures, further refined by restrained molecular dynamics using a simulated annealing protocol in the AMBER force field, with a backbone r.m.s.d. for the well defined Glu3-Cys28 segment of 0.69(+/-0.12) angstroms. The main structural element is an antiparallel beta-sheet from Met13 to Lys23 including a betaI-turn over Gln17-Phel8 with a beta bulge at Gly19. In addition, a beta'I turn over Arg6-Gly7, a beta'III turn over Ser11-Gly12 and a helical turn from Gly24 to Cys28 are identified. This structure is very similar to the equivalent regions of the X-ray structure of wheat germ agglutinin and the NMR structure of hevein.

Alternate JournalJ. Mol. Biol.
PubMed ID8627629