Intermolecular exchange and stabilization of recombinant human alphaA- and alphaB-crystallin.
Lens alpha-crystallin subunits alphaA and alphaB are differentially expressed and have a 3-to-1 ratio in most mammalian lenses by intermolecular exchange. The biological significance of this composition and the mechanism of exchange are not clear. Preparations of human recombinant alphaA- and alphaB-crystallins provide a good system in which to study this phenomenon. Both recombinant alphaA- and alphaB-crystallins are folded and aggregated to the size of the native alpha-crystallin. During incubation together, they undergo an intermolecular exchange as shown by native isoelectric focusing. Circular dichroism measurements indicate that the protein with a 3-to-1 ratio of alphaA- and alphaB-crystallins has the same secondary structure but somewhat different tertiary structures after exchange: the near-UV CD increases after exchange. The resulting hybrid aggregate is more stable than the individual homogeneous aggregates: at 62 degrees C, alphaB-crystallin is more susceptible to aggregation and displays a greater light scattering than alphaA-crystallin. This heat-induced aggregation of alphaB-crystallin, however, was suppressed by intermolecular exchange with alphaA-crystallin. These phenomena are also observed by fast performance liquid chromatography gel filtration patterns. The protein structure of alphaB-crystallin is stabilized by intermolecular exchange with alphaA-crystallin.
Sun
T X
TX
Center for Ophthalmic Research, Brigham and Women's Hospital, and Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts 02115, USA.
Liang
J J
JJ
D002850:Chromatography, Gel; D002853:Chromatography, Liquid; D002942:Circular Dichroism; D003459:Crystallins / Q000737:chemistry*; D006801:Humans; D007223:Infant; D008027:Light; D011994:Recombinant Proteins / Q000737:chemistry; D012542:Scattering, Radiation
D003459:Crystallins; D011994:Recombinant Proteins