Ovine β-lactoglobulin at atomic resolution

Abstract

The crystal structure of the triclinic form of the milk protein β-lactoglobulin from sheep (Ovis aries) at 1.1 Å resolution is described together with a comparison of the triclinic structures of the low-pH bovine and high-pH ovine proteins. All three structures are remarkably similar, despite the well known pH-dependent conformational transition described for the bovine and porcine proteins that occurs in solution. The high resolution of the present structure determination has allowed a more accurate description of the protein than has hitherto been possible, but it is still not clear whether flexibility changes in the external loops can compensate for the presence of a significant void in the unliganded interior of the structure.

Electrostatically Driven Protein Adsorption: Charge Patches versus Charge Regulation

“…Representation of the proteins (as tertiary structure) used in this work. The structures were obtained from crystallographic atomic coordinates taken from the PDB files: hen egg-white lysozyme (in red, IEP: 11.2, PDB ID: 3RZ4), ribonuclease A (RNase, in yellow, IEP: 9.9, PDB ID: 1KF5 ), human salivary α-amylase (in green, IEP: 6.4, PDB ID: 1SMD ), and ovine β-lactoglobulin (in blue, IEP: 5.1, PDB ID: 4CK4 ). The bar shows the scale in angstroms.…”

Structure, Oligomerisation and Interactions of β-Lactoglobulin

“…A study of caprine βLg suggests a comparable dissociation constant as for bovine βLg under similar conditions [18]. Given the high level of sequence identity between caprine and ovine βLg [17], it is likely that ovine βLg exhibits similar oligomerisation behaviour. The nonruminant equine and porcine βLg orthologues, however, are monomeric at physiological pH [21,34].…”

“…Crystal structures of ovine (sheep) [16,17], caprine (goat) [18,19] and reindeer βLg [20] indicate that these orthologues share a high degree of structural similarity with bovine βLg, at both the tertiary and quaternary level (Figure 3), with minimal root-mean-square deviations when aligning the C-α atoms of these structures ( Table 1). However, there are significant differences between the structures of these orthologues and that of porcine βLg, which in the crystal structure features a completely different quaternary association [21].…”

“…The ultrahigh resolution crystal structures of caprine and ovine βLg [17,18] make it possible to clearly define features that in lower resolution bovine and reindeer βLg structures are obscured by disorder and conformational promiscuity. These features include the long flexible CD and GH loops, the C-terminal region, and the AB loops at the dimer interface.…”

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

“…The cow protein now has complete 3-dimensional structural data from pH 2 to 8 ( Khan et al, 2018 ; Yeates and McPherson, 2019 ). Interestingly, the transition is shifted to significantly higher pH in porcine βLg ( Ugolini et al, 2001 ) while the EF loop is also mobile in the protein structures available for sheep ( Kontopidis et al, 2014 ; Loch et al, 2014 ), goat ( Crowther et al, 2014 ; Loch et al, 2015 ), reindeer ( Oksanen et al, 2006 ) and pig ( Hoedemaeker et al, 2002 ). As Glu 89 is very well conserved among the βLg homologues, it may be that there is functional significance in this observed gating ( Qin et al, 1998 ; Ragona et al, 2003 ; Konuma et al, 2007 ; Loch et al, 2019 ), mimicked by simulation ( Bello and García-Hernández, 2014 ; Bello, 2020 ; Fenner et al, 2020 ; Labra-Núñez et al, 2021 ), once again being consistent with a transport function (e.g., Sawyer, 2013 ; Edwards and Jameson, 2020 ).…”