Three-dimensional structure and dynamics of wine tannin-saliva protein complexes. A multitechnique approach.
The interactions between the B3 (catechin-4alpha,8-catechin) red wine tannin and the human salivary protein fragment IB7(14) (SPPGKPQGPPPQGG) were monitored by (1)H magic angle spinning NMR, circular dichroism, electrospray ionization mass spectrometry, and molecular modeling. It is found that the secondary structure of IB7(14) is made of a type II helix (collagen helix) and random coil. The central glycine 8 appears to act as a flexible rotula separating two helix II regions. Three tannin molecules tightly complex the peptide, without modifying its secondary structure, but seem to reduce its conformational dynamics. The binding dissociation constant is in the millimolar range. B3 tannins with a "tweezers" conformation bind to the hydrophilic side of the saliva peptide, suggesting that the principal driving forces toward association are governed by hydrogen bonding between the carbonyl functions of proline residues and both the phenol and catechol OH groups. These findings are further discussed in the frame of an astringency phenomenon.
Simon
Cécile
C
Institut Européen de Chimie et Biologie, UMR CNRS 5144, Pessac, France.
Barathieu
Karine
K
Laguerre
Michel
M
Schmitter
Jean-Marie
JM
Fouquet
Eric
E
Pianet
Isabelle
I
Dufourc
Erick J
EJ
D000872:Anthocyanins / Q000737:chemistry* / Q000378:metabolism; D002942:Circular Dichroism; D006801:Humans; D046911:Macromolecular Substances; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008958:Models, Molecular; D015394:Molecular Structure; D010446:Peptide Fragments / Q000737:chemistry* / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012471:Salivary Proteins and Peptides / Q000737:chemistry* / Q000378:metabolism; D014920:Wine
D000872:Anthocyanins; D046911:Macromolecular Substances; D010446:Peptide Fragments; D012471:Salivary Proteins and Peptides; C427205:proanthocyanidin B3; C478131:salivary protein fragment IB7(14), human