Ecroyd, H.Meehan, S.Horwitz, J.Aquilina, J.Benesch, J.Robinson, C.MacPhee, C.Carver, J.2008-04-302008-04-302007Biochemical Journal, 2007; 401 Part 1(1):129-1410264-60211470-8728http://hdl.handle.net/2440/42949Copyright © 2007 The Biochemical Society, LondonαB-crystallin is a member of the sHsp (small heat-shock protein) family that prevents misfolded target proteins from aggregating and precipitating. Phosphorylation at three serine residues (Ser19, Ser45 and Ser59) is a major post-translational modification that occurs to αB-crystallin. In the present study, we produced recombi-nant proteins designed to mimic phosphorylation of αB-crystallin by incorporating a negative charge at these sites. We employed these mimics to undertake a mechanistic and structural invest-igation of the effect of phosphorylation on the chaperone activity of aB-crystallin to protect against two types of protein misfolding, i.e. amorphous aggregation and amyloid fibril assembly. We show that mimicking phosphorylation of αB-crystallin results in more efficient chaperone activity against both heat-induced and reduc-tion-induced amorphous aggregation of target proteins. Mimick-ing phosphorylation increased the chaperone activity of αB-crystallin against one amyloid-forming target protein (k-casein), but decreased it against another (ccb-Trp peptide). We observed that both target protein identity and solution (buffer) conditions are critical factors in determining the relative chaperone ability of wild-type and phosphorylated αB-crystallins. The present study provides evidence for the regulation of the chaperone activity of αB-crystallin by phosphorylation and indicates that this may play an important role in alleviating the pathogenic effects associated with protein conformational diseases.enJournal article002007008610.1042/BJ200609810002435388000142-s2.0-3384627838249316