THE APPARENT MOLECULAR-SIZE OF NATIVE ALPHA-CRYSTALLIN-B IN NONLENTICULAR TISSUES

The apparent molecular size of the native α-crystallin B in cytosol preparations from rat heart, brain and retina was determined by gel permeation chromatography, detecting the protein by immunochemical assay (ELISA), using an α-crystallin specific antiserum. Native α-crystallin from cytosol preparations of rat lens cortex was used as a reference. α-Crystallin B present in all three cytosol preparations from non-lenticular tissues eluted in a single symmetrical peak, with the same elution volume as α-crystallin from lens cortex cytosol preparations, corresponding to an apparent average molecular size of 0.8 × 106 Da. No other species could be detected. The results indicate that the α-crystallin aggregates characterized by an apparent average molecular mass of 0.8 × 106 Da, and considered to be the native, physiological form of the protein in the lens, are indeed not specific to lens tissue. Furthermore, the size of these α-crystallin aggregates is independent of their polypeptide composition. Aggregates found in the lens, composed of αA and αB polypeptides and their respective phosphorylated forms αAp and αBp, are similar in size to those found in heart, brain and retina, containing the αB but not the αA polypeptide. © 1990.