Native quaternary structure of bovine alpha-crystallinNative quaternary structure of bovine alpha-crystallin
Faculty of Pharmaceutical, Biomedical and Veterinary Sciences . Biomedical Sciences
Department of Biomedical Sciences
2000Washington, D.C., 2000
Biochemistry / American Chemical Society. - Washington, D.C., 1962, currens
39(2000):15, p. 4483-4492
University of Antwerp
alpha-Crystallin is the most important soluble protein in the eye lens. It is responsible for creating a high refractive index and is known to be a small heat-shock protein. We have used static and dynamic light scattering to study its quaternary structure as a function of isolation conditions, temperature, time, and concentration. We have used tryptophan fluorescence to study the temperature dependence of the tertiary structure and its reversibility, Gel filtration, analytical ultracentrifugation, polyacrylamide gel electrophoretic analysis, and absorption measurements were used to study the chaperonelike activity of a-crystallin in the presence of destabilized lysozyme. We have demonstrated that the molecular mass of the in vivo alpha-crystallin oligomer is about 700 kDa (alpha(native)) while the 550 kDa molecule (alpha(37 degrees C,diluted)), which is often found in vitro, is a product of prolonged storage at 37 degrees C of low concentrated alpha-crystallin solutions. We have proven that the molecular mass of the alpha-crystallin oligomer is concentration dependent at 37 degrees C. We have found strong indications that, during chaperoning, the alpha-crystallin oligomer undergoes a drastic rearrangement of its peptides during the process of complex formation with destabilized lysozyme. We propose the hypothesis that all these processes are governed by the phenomenon of subunit exchange, which is well-known to be strongly temperature-dependent.