Human lens high-molecular-weight alpha-crystallin aggregates.
Alpha-crystallin high-molecular-weight (HMW) aggregates can be formed in vitro by many mechanisms, but the mechanism of in vivo aggregation has not been clearly established. HMW and LMW (low-molecular-weight) alpha-crystallins were isolated from human lenses 50-60 years of age and some spectroscopic measurements were performed. Conformational differences were suggested based on data of increased bis-ANS (4,4'-dianilino-1,1'-binaphthalene-5, 5'-disulfonic acid) and ThT (thioflavin T) fluorescence as well as increased far-UV and decreased near-UV circular dichroism (CD). These results indicated that HMW alpha-crystallin was more hydrophobic than LMW alpha-crystallin, possibly resulting from partial unfolding of alpha-crystallin. On the other hand, the increased ThT fluorescence and far-UV CD intensities indicate that an increased 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 aggregates resulted from partial unfolding and disassembling-reassembling of LMW alpha-crystallin caused by posttranslational modification rather than chaperone complex formation.
Liang
J J
JJ
Center for Ophthalmic Research, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA. jliang@rics.bwh.harvard.edu
Akhtar
N J
NJ
D018833:Chaperonins / Q000737:chemistry / Q000378:metabolism; D002853:Chromatography, Liquid; D002942:Circular Dichroism; D003459:Crystallins / Q000737:chemistry* / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007908:Lens, Crystalline / Q000737:chemistry*; D008970:Molecular Weight; D013050:Spectrometry, Fluorescence
D003459:Crystallins; D018833:Chaperonins