Exploring the Aggregation Propensity of γS-Crystallin Protein Variants Using Two-Dimensional Spectroscopic Tools

The
formation of amyloid fibrils is associated with many serious diseases
as well as diverse biological functions. Despite the importance of
these aggregates, predicting the aggregation propensity of a particular
sequence is a major challenge. We report a joint 2D nuclear magnetic
resonance (NMR) and ultraviolet (2DUV) study of fibrillization in
the wild-type and two aggregation-prone mutants of the eye lens protein
γS-crystallin. Simulations show that the complexity of 2DUV
signals as measured by their “approximate entropy” is
a good indicator for the conformational entropy and in turn is strongly
correlated with its aggregation propensity. These findings are in
agreement with high-resolution NMR experiments and are corroborated
for amyloid fibrils. The 2DUV technique is complementary to high-resolution
structural methods and has the potential to make the evaluation of
the aggregation propensity for protein variant propensity of protein
structure more accessible to both theory and experiment. The approximate
entropy of experimental 2DUV signals can be used for fast screening,
enabling identification of variants with high fibrillization propensity
for the much more time-consuming NMR structural studies, potentially
expediting the characterization of protein variants associated with
cataract and other protein aggregation diseases.