Human lens high-molecular-weight alpha-crystallin aggregates

alpha-crystallin high-molecular-weight (HMW) aggregates can be formed in vi tro by many mechanisms, but the mechanism of in vivo aggregation has not be en clearly established. HMW and LMW (low-molecular-weight) alpha-crystallin s were isolated from human lenses 50-60 years of age and some spectroscopic measurements were performed, Conformational differences were suggested bas ed on data of increased bis-ANS (4,4'-dianilino-1,1'-binaphthalene-5,5'-dis ulfonic acid) and ThT (thioflavin T) fluorescence as well as increased far- UV and decreased near-UV circular dichroism (CD). These results indicated t hat HMW alpha-crystallin was more hydrophobic than LMW cu-crystallin, possi bly resulting from partial unfolding of a-crystallin. On the other hand, th e increased ThT fluorescence and far-UV CD intensities indicate that an inc reased amount of beta-sheet conformation was involved in aggregation. These data, along with little difference in chaperone-like activity between the LMW and HMW alpha-crystallins, strongly suggest that HMW alpha-crystallin a ggregates resulted from partial unfolding and disassembling-reassembling of LMW alpha-crystallin caused by posttranslational modification rather than chaperone complex formation. (C) 2000 Academic Press.