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Interaction and aggregation of lens crystallins.
1Howe Laboratory of Ophthalmology, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston 02114.
Experimental Eye Research
|July 1, 1991
Summary
Eye lens crystallins maintain transparency through structure. Age-related changes cause aggregation and opacity, which this study investigated using fluorescence. Alpha-crystallin aggregation is linked to increased hydrophobicity.
Area of Science:
- Biochemistry
- Ophthalmology
- Protein Chemistry
Background:
- Eye lens transparency relies on specific crystallin structure maintained by short-range order.
- Age-related post-translational modifications and high molecular weight (HMW) aggregation disrupt this structure, leading to decreased lens transparency.
Purpose of the Study:
- To investigate protein interactions and aggregation mechanisms in eye lens crystallins using fluorescence spectroscopy.
- To understand the role of hydrophobicity in the aggregation of alpha-crystallin.
Main Methods:
- Fluorescence polarization measurements using dansyl chloride (DCl) labeled gamma-crystallin.
- Extrinsic probe binding assays with hydrophobic probes like ANS (1-anilinonaphthalene-8-sulfonic acid) and DPH (1,6-diphenyl 1,3,5-hexatriene).
Main Results:
- Gamma-crystallin exhibits hetero-interactions (e.g., alpha-gamma, beta-gamma) but not self-interaction at concentrations below 30 mg/ml.
- Alpha-crystallin is highly hydrophobic, with HMW alpha-crystallin showing increased hydrophobicity, suggesting exposed hydrophobic groups facilitate aggregation.
- HMW aggregation is driven by highly hydrophobic proteins seeking thermodynamic stability.
Conclusions:
- Protein-protein interactions and hydrophobicity play critical roles in maintaining lens transparency and in the pathological aggregation of crystallins.
- Post-translational modifications exposing hydrophobic regions are key drivers of HMW aggregation in alpha-crystallin, contributing to age-related lens opacities.