Abstract
Abstract: :
Purpose: To characterize the physical parameters of alpha-crystallin throughout adult human lenses and to correlate these with the posttranslational modifications of alpha crystallins. Methods: Adult normal human eyes (39, 46, 52, 54, and 69 yr ) were obtained from NDRI. The lenses were removed and dissected into successive layers of fiber cells. The samples from one lens of a pair were analyzed by electrophoresis, while the soluble proteins from the other were extracted by standard methods and fractionated on a FPLC Superose 6 gel filtration column. Results: For each lens age, alpha crystallin was distributed between two peaks, Peak 1 (high molecular weight) and Peak 2 (low molecular weight). With increasing depth in each lens, there was a progressive shift from low molecular weight Peak 2 species to high molecular weight peak 1 species. The outer cortex regions of all five lenses exhibit similar profiles; all of the protein is present in the low molecular weight peak. Likewise, the profiles from the lens nuclear samples were all similar; protein was present only as high molecular weight species and the relative amount of protein was very low. The protein in samples from the inner cortex at each age was present as species varying in size from the low molecular weight to the high molecular weight species; the distribution showed some dependence on age of the lens. Previous electrophoretic studies showed progressive posttranslational modification of the alpha crystallins that correspond to changes in aggregate size seen in this study. Conclusions: Temporal and spatial changes in alpha-crystallin are associated with both patterned post-translational modifications of the protein and patterned alteration of aggregate size and state.
Keywords: 378 crystallins • 525 protein modifications-post translational • 527 protein structure/function