Structural Changes in α-Crystallin and Whole Eye Lens During Heating, Observed by Low-angle X-ray Diffraction

• Published in: Journal of molecular biology Vol. 336; no. 5; pp. 1185 - 1194
• Main Authors: Regini, J.W., Grossmann, J.G., Burgio, M.R., Malik, N.S., Koretz, J.F., Hodson, S.A., Elliott, G.F.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 05.03.2004
• Subjects: alpha-Crystallins - chemistry; Animals; eye; Gels; Hot Temperature; lens; Lens, Crystalline - chemistry; Protein Conformation; Rabbits; Solutions; Temperature; X-Ray Diffraction - methods; X-ray scattering; α-crystallin; eye; temperature; X-ray scattering; α-crystallin; lens
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1016/S0022-2836(03)00814-3

Whole eye lens and α-crystallin gels and solutions were investigated using X-ray scattering techniques at temperatures ranging from 20 °C to 70 °C. In whole lens isolated in phosphate-buffered saline, the spacing of the dominant X-ray reflection seen with low-angle scattering was constant from 20 °C to 45 °C but increased at 50 °C from 15.2 nm to 16.5 nm. At room temperature, the small-angle X-ray diffraction pattern of the intact lens was very similar to the pattern of α-crystallin gels at near-physiological concentration (≈300 mg/ml), so it is reasonable to assume that the α-crystallin pattern dominates the pattern of the intact lens. Our results therefore indicate that in whole lens α-crystallin is capable of maintaining its structural properties over a wide range of temperature. This property would be useful in providing protection for other lens proteins super-aggregating. In the α-crystallin gels, a moderate increase in both the spacing and intensity of the reflection was observed from 20 °C to 45 °C, followed by an accelerated increase from 45 °C to 70 °C. Upon cooling, this effect was found to be irreversible over 11 hours. Qualitatively similar results were observed for α-crystallin solutions at a variety of lower concentrations.