Abstract
Grape thaumatin-like proteins (TLPs) play roles in plant-pathogen interactions and can cause protein haze in white wine unless removed prior to bottling. Different isoforms of TLPs have different hazing potential and aggregation behavior. Here we present the elucidation of the molecular structures of three grape TLPs that display different hazing potential. The three TLPs have very similar structures despite belonging to two different classes (F2/4JRU is a thaumatin-like protein while I/4L5H and H2/4MBT are VVTL1), and having different unfolding temperatures (56 vs. 62°C), with protein F2/4JRU being heat unstable and forming haze, while I/4L5H does not. These differences in properties are attributable to the conformation of a single loop and the amino acid composition of its flanking regions.
Highlights
Securing wine stability is essential in winemaking
The three thaumatin-like proteins isolated from Vitis vinifera shared significant sequence similarity to the banana thaumatin-like protein (1Z3Q), the structure of which has been solved [22]
The proteins responsible for haze formation in wines are derived from grape juice [44]
Summary
Securing wine stability is essential in winemaking. Among the possible instabilities that can occur, protein haze formation is the most important instability of nonmicrobial origin, for white wine production [1, 2]. Vitis vinifera grape juices and wines generally contain between 10 and 500 mg/L of protein [3]. Despite these low concentrations, proteins have a great technological relevance in winemaking as some of them, the grape pathogenesis-related (PR) proteins, can aggregate to form a visible haze [4, 5]. The grape PR proteins [2] are constitutively.
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