Heat treatment of small heat shock proteins α-crystallin and Hsp 16.3: Structural changes vs. chaperone-like activity

Both α-crystall in from bovine eye lens and Hsp l6.3 from Mycobacterium tuberculosis are members of the small heat shock protein family. They were preincubated at 100 for 15 mn and then cooled on ice immediately. The chaperone-like activities of preheated proteins were measured at 37 using DTT-treated insulin B chains as substrates. Both preheated proteins exhibited greatly enhanced chaperone-like activities, accompanied with almost unchanged secondary structures and surface hydrophobicity but with a minor change in tertiary structures. The dramatically enhanced chaperone-like activities of preheated α-crystallin and Hspl6. 3 may have resulted from the imeversible change in the tertiary structure as detected by near-UV CD spectra.