Analysis of Global and Residue‐Specific yB Crystallin Protein Dynamics via NMR Spectroscopy and Dynamic Light Scattering

Abstract

The proteins that comprise the water‐soluble interior of the optic lens are referred to as crystallin proteins, of which three major categories have been identified: alpha (a), beta (b), and gamma (y). Gamma and beta crystallin proteins have been observed to undergo aggregation and phase‐separation over time, which can lead to the formation of cataracts, while alpha crystallin limits this formation by removing deformed protein aggregates from solution. Here, we describe our studies on bovine yB crystallin, which is the homologue to human yD crystallin. To better understand the intermolecular interactions between yB crystallins, we overexpressed the 15N‐labeled recombinant protein in Escherichia coli, purified it via column chromatography, and studied the effect of solution conditions on protein dynamics using NMR spectroscopy and dynamic light scattering techniques. Prior research from our group employed T1‐T2 NMR experiments to probe the effect of temperature and protein concentration on global protein dynamics, while more recent 1H‐15N HSQC experiments allowed us to visualize the amide proton peaks for yB crystallin protein at various concentrations. We observed small peak shifts for select residues as the protein concentration increased, which we hypothesized were due to increased intermolecular interactions between yB crystallin molecules. Analysis of these NMR spectra, combined with dynamic light scattering data on the same samples, provide further insight into both global dynamics as well as residue‐specific interactions.