Monomerization and aggregation of β-Lactoglobulin under adverse condition: A fluorescence correlation spectroscopic investigation

Publication date: Available online 15 November 2017 Source:Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics Author(s): Bhaswati Sengupta, Nilimesh Das, Pratik Sen β-lactoglobulin is one of the major components of bovine milk and it remains in a dimeric form under physiological conditions. The present contribution elucidates the structural change of β-lactoglobulin at pH7.4 under the action of guanidine hydrochloride (GnHCl) and heat at the single molecular level. The only free cysteine (Cys-121) of β-lactoglobulin has been tagged with 7-Diethylamino-3-(4-maleimidophenyl)-4-methylcoumarin (CPM) for this purpose. The dimeric structure of β-lactoglobulin found to undergoes a monomerization prior to the unfolding process upon being subjected to GnHCl. The hydrodynamic diameter of the native dimer, native monomer and the unfolded monomer has been estimated as ~55Å, ~29Å and ~37Å, respectively. The free energy change for the monomerization and denaturation are respectively 1.57kcal mol−1 and 8.93kcal mol−1. With change in temperature, development of two types of aggregates (small aggregates and large aggregates) was observed, which is triggered by the formation of the monomeric structure of β-lactoglobulin. The hydrodynamic diameters of the smaller and larger aggregates has been estimated to be ~77Å and ~117Å, respectively. The formation of small aggregates turns out to be reversible whereas that of larger aggregates is irreversible. The free energy ...

Source: Biochimica et Biophysica Acta (BBA) Proteins and Proteomics - November 16, 2017 Category: Biochemistry Source Type: research