Heat-induced denaturation of cataract-related human γ D-crystallin
Objective To reveal the thermally induced denaturation of wild-type human γ D-crystallin(HGD)and congenital cataract-related mutant(HGD P23T),and compare the differences in the structural changes between wild-type and mutants during a heating process.Methods HGD and HGD P23T were expressed and purified.The temperature-dependent intrinsic fluorescence intensity and static light scattering intensity of the protein samples were measured to reveal the temperature-dependent folding and aggregation structural changes of HGD and HGD P23T.Results When the temperature was below 70℃,the barycentric mean of the intrinsic fluorescence of HGD and HGD P23T shifted towards a longer wavelength with increasing temperature and the fluorescence intensity de-creased indicating the unfolded protein conformations.The conformational stability of HGD P23T was weaker than that of HGD.When temperature was higher than 70℃,the static light scattering intensity increased significantly with temperature,indicating protein aggregation upon heating.Relative to the wild-type,HGD P23T showed a stronger aggregation potency.Conclusions Heating disrupts the folding conformation of Γd-crystallin,induces the unfolded protein to aggregate.The disease-associated P23T mutation significantly reduces the conformational stability of Γd-crystallin.
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