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Human lens high-molecular-weight alpha-crystallin aggregates
1Center for Ophthalmic Research, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA. jliang@rics.bwh.harvard.edu
Biochemical and Biophysical Research Communications
|August 31, 2000
Summary
High-molecular-weight (HMW) alpha-crystallin aggregates in human lenses likely form from partial unfolding and reassembly of low-molecular-weight (LMW) alpha-crystallins due to posttranslational modification, not chaperone activity.
Area of Science:
- Biochemistry
- Ophthalmology
- Protein Chemistry
Background:
- Alpha-crystallins are crucial lens proteins, and their aggregation into high-molecular-weight (HMW) forms is implicated in cataracts.
- The in vivo mechanisms driving HMW alpha-crystallin aggregation remain incompletely understood.
Purpose of the Study:
- To investigate the structural and conformational differences between HMW and low-molecular-weight (LMW) alpha-crystallins isolated from human lenses.
- To elucidate the aggregation mechanism of HMW alpha-crystallins in vivo.
Main Methods:
- Isolation of HMW and LMW alpha-crystallins from human lenses (50-60 years of age).
- Spectroscopic analyses including bis-ANS and Thioflavin T (ThT) fluorescence, far-UV, and near-UV circular dichroism (CD).
- Assessment of chaperone-like activity.
Main Results:
- HMW alpha-crystallin exhibited increased hydrophobicity and beta-sheet content compared to LMW alpha-crystallin, suggesting partial unfolding.
- Increased ThT fluorescence and far-UV CD indicated a greater proportion of beta-sheet structure in HMW aggregates.
- Chaperone-like activity showed minimal difference between HMW and LMW forms.
Conclusions:
- HMW alpha-crystallin aggregates likely arise from posttranslational modification-induced partial unfolding and subsequent disassembling-reassembling of LMW alpha-crystallins.
- The aggregation process appears independent of chaperone complex formation.