Thermodynamic stability of human lens recombinant alphaA- and alphaB-crystallins.
Lens alpha-crystallin is a 600-800-kDa heterogeneous oligomer protein consisting of two subunits, alphaA and alphaB. The homogeneous oligomers (alphaA- and alphaB-crystallins) have been prepared by recombinant DNA technology and shown to differ in the following biophysical/biochemical properties: hydrophobicity, chaperone-like activity, subunit exchange rate, and thermal stability. In this study, we studied their thermodynamic stability by unfolding in guanidine hydrochloride. The unfolding was probed by three spectroscopic parameters: absorbance at 235 nm, Trp fluorescence intensity at 320 nm, and far-UV circular dichroism at 223 nm. Global analysis indicated that a three-state model better describes the unfolding behavior than a two-state model, an indication that there are stable intermediates for both alphaA- and alphaB-crystallins. In terms of standard free energy (DeltaG(NU)(H(2)(O))), alphaA-crystallin is slightly more stable than alphaB-crystallin. The significance of the intermediates may be related to the functioning of alpha-crystallins as chaperone-like molecules.
Sun
T X
TX
Center for Ophthalmic Research, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
Akhtar
N J
NJ
Liang
J J
JJ
D000817:Anilino Naphthalenesulfonates / Q000737:chemistry; D002853:Chromatography, Liquid / Q000379:methods; D003459:Crystallins / Q000737:chemistry*; D006801:Humans; D007700:Kinetics; D008027:Light; D017510:Protein Folding; D011994:Recombinant Proteins / Q000737:chemistry; D012542:Scattering, Radiation; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics
D000817:Anilino Naphthalenesulfonates; D003459:Crystallins; D011994:Recombinant Proteins; C027132:1-anilino-8-naphthalenesulfonate