Stable monomeric intermediate with exposed Cys-119 is formed during heat denaturation of β-lactoglobulin

Thomas Croguennec (1) , Said Bouhallab (1) , Daniel Mollé (1) , Brendan T. O’kennedy (2) , Raj Mehra (2)

1 STLO - Science et Technologie du Lait et de l'Oeuf
2 Dairy Products Research Center

The role of the free sulfhydryl group of b-lactoglobulin in the formation of a stable non-native monomer during heat-treatment of b-lactoglobulin solutions was investigated. Two concomitant events occurred at the earlier stage of heating: unfolding of native globular monomer and intramolecular sulfhydryl/disulfide exchange reaction. Thus, two denatured monomeric species were formed: a non-native monomer with exposed Cys-121 (Mcys121) which became reversible after cooling, and a stable non-native monomer with exposed Cys-119 (Mcys119) which exhibited both a larger hydrodynamic conformation than native monomer and low solubility at pH 4.7. The results also show that the formation of these monomeric species throughout heat-induced denaturation of native b-lg monomers is faster than their subsequent aggregation. A mechanism describing the behavior of b-lg denaturation/aggregation during heat-treatment under selected conditions (5.8 mg/ml, low ionic strength, pH 6.6, 85 °C) is presented.

Mots clés: beta-Lactoglobuline; N-Ethylmaleimide; traitement thermique; dénaturation; Sulfhydryl group; Stable non-native monomer; ²-lactoglobulin; sulphydryl compounds

Mots clés: dénaturation des protéines; composition monomérique; traitement thermique de l'aliment; beta lactoglobuline; N Ethylmaleimide; composé organosoufre; Sulfhydryl

Domaines: Ingénierie des aliments; Alimentation et Nutrition

Thomas Croguennec, Said Bouhallab, Daniel Mollé, Brendan T. O’kennedy, Raj Mehra. Stable monomeric intermediate with exposed Cys-119 is formed during heat denaturation of β-lactoglobulin. Biochemical and Biophysical Research Communications, 2003, 301 (2), pp.465-471. ⟨10.1016/S0006-291X(02)02997-2⟩. ⟨hal-01569504⟩