Structure, Oligomerisation and Interactions of β-Lactoglobulin

Abstract

β-Lactoglobulin (βLg), as the most abundant whey protein in ruminant milk and as a useful model protein, is the subject of countless biophysical studies in the literature, yet its physiological role is hitherto unknown. This chapter deals with studies that focus on the structure of βLg, its oligomeric behaviour and the interactions that this protein participates in. These and further studies are necessary to understand how the protein's physicochemical properties may influence the processing, digestion and immunogenicity of ruminant milks and their products. However, there is also a need for research into the interactions that occur naturally between βLg and other components in milk, as this may give us insight into the physiological role of the protein.

Formation and Characterization of β-Lactoglobulin and Gum Arabic Complexes: the Role of pH

“…One monomer of bovine β-Lg contains eight β-strands that form the central antiparallel β-sheet calyx and a ninth β-strand that is involved in dimer formation. Each monomer contains five cysteine residues and four of them form two disulfide bridges to fold β-Lg [ 29 ]. A molecule of free β-Lg had a hydrodiameter of about 4.86 nm and the diameter reduced to 2 nm in solution at medium pH at room temperature.…”

Determination of specific and non-specific protein–protein interactions for beta-lactoglobulin by analytical ultracentrifugation and membrane osmometry experiments

“…66 The reconstructed structures were protonated at pH = 3 and pH = 7 using PROPKA method 67 (version 3.3) and PDB2PQR online webserver. 68 This resulted in the charge of the BLG monomer of +18 e − and −8 e − 69 at pH 3 and pH 7, respectively (while experimentally determined charges are +20 e at pH 2.5 and −9 e at pH 7.5). 69 The reconstructed and protonated all-atom structures were used to map the BLG into the CG representation (Fig.…”

“…68 This resulted in the charge of the BLG monomer of +18 e − and −8 e − 69 at pH 3 and pH 7, respectively (while experimentally determined charges are +20 e at pH 2.5 and −9 e at pH 7.5). 69 The reconstructed and protonated all-atom structures were used to map the BLG into the CG representation (Fig. 1; variant BLG-A).…”

β-Lactoglobulin and Glycodelin: Two Sides of the Same Coin?

“…The ruminant βLgs are dimers at around neutral pH but become monomeric at low pH (Timasheff and Townend, 1961;Zimmerman et al, 1970;Joss and Ralston, 1996;Mercadante et al, 2012;Khan et al, 2018). The dimer interface involves the antiparallel arrangement of β-strand I as well as other interactions and crystal structures reported over a wide range of pH show that the interface is flexible (Vijayalakshmi et al, 2008;Crowther et al, 2016). Porcine βLg on the other hand is dimeric at low pH and monomeric around neutrality (Ugolini et al, 2001) with a completely different, domain-swapping dimerization (Hoedemaeker et al, 2002).…”