Title:H101G Mutation in Rat Lens αB-Crystallin Alters Chaperone Activity and
Divalent Metal Ion Binding
Volume: 23
Issue: 5
Author(s): Yi-Ying Wu, Naveen Kumar Reddy Desu, Shou-Yun Lu, Bi-Yu Yu, Ramya Kumar and Fu-Yung Huang*
Affiliation:
- Department of Chemistry, National Cheng Kung University, Tainan, Taiwan
Keywords:
αB-crystallin, chaperone activity, hydrophobicity, site-directed mutagenesis, circular dichroism, far-UV CD spectra.
Abstract: Background: The molecular chaperone function of αB-crystallins is heavily involved in
maintaining lens transparency and the development of cataracts.
Objectives: The aim of the study was to investigate whether divalent metal ion binding improves the
stability and αB-crystallin chaperone activity.
Methods: In this study, we have developed an H101G αB-crystallin mutant and compared the
surface hydrophobicity, chaperone activity, and secondary and tertiary structure with the wild type
in the presence and absence of metal ions.
Results: Substitution of His101 with glycine resulted in structural and functional changes. Spectral
analysis and chaperone-like activity assays showed that substitution of glycine resulted in a higher
percentage of random coils, increased hydrophobicity, and 22±2% higher chaperone-like activity.
Whereas in the presence of the Cu2+ ion, H101G exhibited 32±1% less chaperone-like activity
compared to the wild type.
Conclusion: Cu2+ has been reported to enhance the chaperone-like activity of lens α-crystallin. Our
results indicate that H101 is the predominant Cu2+ binding site, and the mutation resulted in a
partial unfolding that impaired the binding of Cu2+ to H101 residue. In conclusion, this study
further helps to understand the important binding site for Cu2+ to αB-crystallin.