SAXS and SANS observations of abnormal aggregation of human •-crystallin

Aggregation states of human α-crystallins are observed complementarily using small-angle X-ray and small-angle neutron scatterings (SAXS and SANS). Infant α-crystallin is almost a monodispersed system of the aggregates with gyration radius of ca. 60 Å, which is a normal aggregate. On the other hand, the aged and cataract α-crystallins have not only the normal but also the larger aggregates. In the aged alpha;-crystallin, the normal aggregate is a major component, but in the cataract α-crystallin the larger ones are dominant. Both αA- and alpha;B-crystallins, which are subunits of α-crystallin, also form an aggregate with the size close to the normal aggregate. Under UV irradiation, only aggregates of αB-crystallin undergo further aggregation. Therefore, considering increase of ratio of αB-crystallin in the aggregate of alpha;-crystallin as aging, the abnormal aggregation (formation of the huge aggregates) mainly results in the further aggregation of alpha;B-crystallin caused by external stresses.