Tannin-assisted aggregation of natively unfolded proteins

D. Zanchi; T. Narayanan; D. Hagenmuller; A. Baron; S. Guyot; B. Cabane; S. Bouhallab

doi:doi:10.1209/0295-5075/82/58001

EPL, 82 (2008) 58001
DOI: 10.1209/0295-5075/82/58001

Tannin-assisted aggregation of natively unfolded proteins

D. Zanchi¹, T. Narayanan², D. Hagenmuller¹, A. Baron³, S. Guyot³, B. Cabane⁴ and S. Bouhallab⁵

¹ Laboratoire de Physique Théorique et Hautes Energies - 4 Place Jussieu, BP 126, F-75252 Paris Cédex 05, France, EU
² European Synchrotron radiation Facility - 6 rue Jules Horowitz, BP 220, F-38043 Grenoble, France, EU
³ UR117 Cidricoles et Biotransformation des Fruits et Légumes, INRA - F-35650 Le Rheu, France, EU
⁴ Laboratoire de Physique et Mécanique des Milieux Hétérogènes, École Supérieure de Physique et de Chimie Industrielles de la Ville de Paris - 10 rue Vauquelin, F-75231 Paris Cédex 05 - France, EU
⁵ INRA, Agrocampus, UMR1253 STLO - 65 rue de Saint Breuc, F-35000 Rennes, France, EU

drazen@lpthe.jussieu.fr

received 10 March 2008; accepted in final form 15 April 2008; published June 2008
published online 23 May 2008

Abstract
Tannin-protein interactions are essentially physical: hydrophobic and hydrogen-bond $\hbox{--}$ mediated. We explored the tannin-assisted protein aggregation on the case of $\beta$ -casein, which is a natively unfolded protein known for its ability to form micellar aggregates. We used several tannins with specified length. Our SAXS results show that small tannins increase the number of proteins per micelle, but keeping their size constant. It leads to a tannin-assisted compactization of micelles. Larger tannins, with linear dimensions greater than the crown width of micelles, lead to the aggregation of micelles by a bridging effect. Experimental results can be understood within a model where tannins are treated as effective enhancers of hydrophobic attraction between specific sites in proteins.