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Exploring the aggregation propensity of ?S-crystallin protein variants using two-dimensional spectroscopic tools.

ABSTRACT: 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 ?S-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.

SUBMITTER: Jiang J

PROVIDER: S-EPMC3946429 | biostudies-literature | 2013 Nov

REPOSITORIES: biostudies-literature

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Exploring the aggregation propensity of γS-crystallin protein variants using two-dimensional spectroscopic tools.

Jiang Jun J Golchert Kory J KJ Kingsley Carolyn N CN Brubaker William D WD Martin Rachel W RW Mukamel Shaul S

The journal of physical chemistry. B 20131112 46

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 ...[more]

PMID: 24219230

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Project description:BackgroundThe eye lens crystallins are highly soluble proteins that are required to last the lifespan of an organism due to low protein turnover in the lens. Crystallin aggregation leads to formation of light-scattering aggregates known as cataract. The G18V mutation of human ?S-crystallin (?S-G18V), which is associated with childhood-onset cataract, causes structural changes throughout the N-terminal domain and increases aggregation propensity. The holdase chaperone protein ?B-crystallin does not interact with wild-type ?S-crystallin, but does bind its G18V variant. The specific molecular determinants of ?B-crystallin binding to client proteins is incompletely charcterized. Here, a new variant of ?S, ?S-G18A, was created to test the limits of ?B-crystallin selectivity.MethodsMolecular dynamics simulations were used to investigate the structure and dynamics of ?S-G18A. The overall fold of ?S-G18A was assessed by circular dichroism (CD) spectroscopy and intrinsic tryptophan fluorescence. Its thermal unfolding temperature and aggregation propensity were characterized by CD and DLS, respectively. Solution-state NMR was used to characterize interactions between ?B-crystallin and ?S-G18A.Results?S-G18A exhibits minimal structural changes, but has compromised thermal stability relative to ?S-WT. The placement of alanine, rather than valine, at this highly conserved glycine position produces minor changes in hydrophobic surface exposure. However, human ?B-crystallin does not bind the G18A variant, in contrast to previous observations for ?S-G18V, which aggregates at physiological temperature.Conclusions?B-crystallin is capable of distinguishing between aggregation-prone and function-preserving variants, and recognizing the transient unfolding or minor conformers that lead to aggregation in the disease-related variant.General significanceHuman ?B-crystallin distinguishes between highly similar variants of a structural crystallin, binding the cataract-related ?S-G18V variant, but not the function-preserving ?S-G18A variant, which is monomeric at physiological temperature.

Dataset Information

Exploring the aggregation propensity of ?S-crystallin protein variants using two-dimensional spectroscopic tools.

Publications

Exploring the aggregation propensity of γS-crystallin protein variants using two-dimensional spectroscopic tools.

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