Comparison of the homologous carboxy-terminal domain and tail of alpha-crystallin and small heat shock protein.

The C-terminal domain and tail, which is the most conserved region of the alpha-crystallin/small heat shock protein (HSP) family, was obtained from rat alpha A-crystallin, bovine alpha B-crystallin and mouse HSP25. All three domains have primarily beta-sheet conformation and less than 10% of alpha-helix, like the proteins from which they are derived. Whereas the C-terminal part of alpha A-crystallin forms dimers or tetramers, the corresponding regions of alpha B-crystallin and HSP25 form larger aggregates. The heat-protective activity, recently described for the alpha-crystallin/small HSP family, is not retained in the C-terminal domain and tail. In the course of this study some differences with the previously published sequence of HSP25 were observed, and a revision is proposed.