Backbone dynamics of bovine [beta]-lactoglobulin by ¹⁵N NMR spectroscopy : a thesis presented in partial fulfillment of the requirements for the degree of Master of Science in Biochemistry, Institute of Fundamental Sciences and Institute of Molecular Biosciences, Massey University, New Zealand

Abstract

Bovine β-lactoglobulin (β-Lg) is a small 162 residue protein of unknown function from the whey component of milk, constituting ~50 % by dry mass. The protein is of great interest to the dairy industry due, in part, to its role in the fouling of dairy plants during heat treatment, and the significant operational costs this incurs. The structure of this protein is an eight stranded β-barrel with one long and two short flanking  helices. It is dimeric at neutral pH but dissociates at pH < 3. In New Zealand herds there are three genetic variants, with variants A and B of bovine β-Lg predominating, while the C variant occurs at low levels in Jersey cows. However, despite the structural similarities of the three variants, milks containing one of A, B or C behaves differently when subjected to thermal processing. A greater understanding of factors that differentiate these protein variants is therefore important. In this study, 15N nuclear magnetic (NMR) spectroscopy methods have been used to study the backbone dynamics of β-Lg A and B, at one temperature, and the hitherto unstudied C variant, at three temperatures. For follow-up functional studies a mutant protein, a covalently linked Ala34Cys dimer, was produced.