Abstract：
:alpha-Crystallin, a major protein of the mammalian lens, plays a vital role in maintaining the structural stability and transparency of the lens. It performs this function through chaperone-like activity; it has recently been reported that heating alpha-crystallin enhances this ability. The present studies, using both time-resolved and steady-state fluorescence methods, were carried out to compare the conformational changes that result from heating with those that result from increasing protein concentration (up to 70 mg/mL). The relative fluorescence quantum yield from tryptophan (Trp) present in alpha-crystallin increases and then decreases with a concomitant shift of the emission maximum to longer wavelengths when either heating times or protein concentrations are increased. The time profile of fluorescence decay was resolved into three components with lifetimes of ca 0.5, 3 and 7 ns and emission maxima of ca 340, 342 and 350 nm, respectively. With longer heating time or increasing concentrations the contribution from the longer-lived component increases at the expense of the shorter-lived species. These data indicate that with heating or at higher concentrations the internal Trp residues move to the surface of the protein giving a more hydrophobic exterior and possibly explain the reported increased chaperone activity upon heating. As a result of the concentration studies, alpha-crystallin may be more efficient in its chaperone activity in vivo than has been determined by in vitro experiments.
journal_name
Photochem Photobioljournal_title
Photochemistry and photobiologyauthors
Mandal K,Dillon J,Gaillard ERdoi
10.1562/0031-8655(2000)071<0470:haceot>2.0.co;2subject
Has Abstractpub_date
2000-04-01 00:00:00pages
470-5issue
4eissn
0031-8655issn
1751-1097journal_volume
71pub_type
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