Enhanced Molecular Chaperone Activity of the Small Heat-Shock Protein αB-Crystallin Following Covalent Immobilization onto a Solid-Phase Support

The well-characterized small heat-shock protein, alpha B-crystallin, acts as a molecular chaperone by interacting with unfolding proteins to prevent their aggregation and precipitation. Structural perturbation (e.g., partial unfolding) enhances the in vitro chaperone activity of alpha B-crystallin. Proteins often undergo structural perturbations at the surface of a synthetic material, which may alter their biological activity. This study investigated the activity of alpha B-crystallin when covalently bound to a support surface; alpha B-crystallin was immobilized onto a range of solid material surfaces, and its characteristics and chaperone activity were assessed. Immobilization was achieved via a plasma-deposited thin polymeric interlayer containing aldehyde surface groups and reductive amination, leading to the covalent binding of alpha B-crystallin lysine residues to the surface aldehyde groups via Schiff-base linkages. Immobilized alpha B-crystallin was characterized by X-ray photoelectron spectroscopy, atomic force microscopy, and quartz crystal microgravimetry, which showed that similar to 300 ng cm(-2) (dry mass) of oligomeric alpha B-crystallin was bound to the surface. Immobilized alpha B-crystallin exhibited a significant enhancement (up to 5000-fold, when compared with the equivalent activity of alpha B-crystallin in solution) of its chaperone activity against various proteins undergoing both amorphous and amyloid fibril forms of aggregation. The enhanced molecular chaperone activity of immobilized alpha B-crystallin has potential applications in preventing protein misfolding, including against amyloid disease processes, such as dialysis-related amyloidosis, and for biodiagnostic detection of misfolded proteins. (C) 2011 Wiley Periodicals, Inc. Biopolymers 95: 376-389, 2011.