Study of human salivary proline-rich proteins interaction with food tannins

- P-B peptide was a salivary protein with a high affinity for procyanidins.
- Acidic proline rich proteins had a lower affinity for procyanidins.
- Procyanidin B2 gallate had the highest affinity for salivary proteins.
- Proline clusters or residues in vicinity identified as probable sites of interaction.
- Acidic and basic proline rich proteins change from extended to coil conformation.

In this work, saturation transfer difference-NMR, isothermal microcalorimetry and molecular dynamics simulations have been used to study the individual interactions between basic, glycosylated and acidic proline-rich proteins (bPRPS, gPRPs, aPRPs) and P-B peptide with some representative food tannins [procyanidin B2, procyanidin B2 3′-O-gallate (B2g) and procyanidin trimer (catechin-4-8-catechin-4-8-catechin)]. Results showed that P-B peptide was in general the salivary protein (SP) with higher affinity whereas aPRPs showed lower affinity to the studied procyanidins. Moreover, B2g was the procyanidin with higher affinity for all SP. Hydrophobic and hydrogen bonds were present in all interactions but the major driving force depended on the procyanidin-SP pair. Furthermore, proline clusters or residues in their vicinity were identified as the probable sites of proteins for interaction with procyanidins. For bPRP and aPRP a significant change to less extended conformations was observed, while P-B peptide did not display any structural rearrangement upon procyanidins binding.