A structural and functional study of Gln147 deamidation in αA-crystallin, a site of modification in human cataract

• Published in: Experimental eye research 2017-08, Vol.161, p.163-173
• Main Authors: Ray, Nicholas J., Hall, Damien, Carver, John A.
• Format: Article
• Language: English
• Subjects: Ageing; alpha-Crystallin A Chain - metabolism; Cataract; Cataract - metabolism; Circular Dichroism; Deamidation; Glutamine - chemistry; Humans; Molecular Chaperones - metabolism; Nuclear Magnetic Resonance, Biomolecular; Post-translational modification; Protein Binding; Protein Processing, Post-Translational; Protein Stability; Spectrometry, Fluorescence; Structure-Activity Relationship; αA-crystallin
• ISSN: 0014-4835; 1096-0007
• DOI: 10.1016/j.exer.2017.05.005

Deamidation of Glu147 in human αA-crystallin is common in aged cataractous lenses (Hains and Truscott, Invest. Ophthalmol. Vis. Sci. 2010, 51, 3107). Accordingly, this modification may have a causative effect in cataract. αA-crystallin is a small heat-shock molecular chaperone protein that prevents aggregation of proteins and is the principal defence against crystallin unfolding and aggregation in the ageing lens. Deamidated Q147E αA-crystallin was structurally characterised using a variety of spectroscopic and biophysical methods, including NMR, circular dichroism and fluorescence spectroscopy and dynamic light scattering. The effect of Glu147 deamidation on αA-crystallin in vitro chaperone ability was determined for a variety of aggregating proteins. Compared to the wild type protein, Q147E αA-crystallin generally exhibited slightly reduced chaperone ability and a small loss of overall structure in its central α-crystallin domain while also showing significantly enhanced thermal stability and a tendency to form slightly larger oligomers. As αA-crystallin is the major lens protein, even a small loss of function could combine with other sources of age-related damage to the crystallins to contribute to lens opacification. •Q147E deamidation of αA-crystallin results in a partial loss molecular of chaperone function.•Q147E deamidation of αA-crystallin causes an increase in protein thermal stability.•Q147E deamidation of αA-crystallin corresponds to an increase in oligomer size.