Kokke BPA et al. (2001) Cell Stress Chaperones "The lack of chaperonelike activity of Caenorhabditis elegans Hsp12.2 cannot be restored by domain swapping with human alphaB-crystallin."

Kokke BP, Boelens WC, Kokke BPA, de Jong WW

[Cell Stress Chaperones, 2001]

The small heat shock proteins Hsp 12.2 and (alphaB-crystallin differ in that the former occurs as tetramers, without chaperonelike activity, whereas the latter forms multimers and is a good chaperone. To investigate whether the lack of chaperone activity of Hspl 2.2 is primarily due to its tetrameric structure or rather to intrinsic sequence features, we engineered chimeric proteins by swapping the N-terminal, C-terminal, and tail regions of Hsp12.2 and alphaB-crystallin, designated as n-c-t and N-C-T, respectively. Three of the chimeric sHsps, namely N-c-T, n-c-T, and N-C-t, showed nativelike secondary and quaternary structures as measured by circular dichroism and gel permeation chromatography. Combining the conserved a-crystallin domain of Hsp12.2 with the N-terminal and tail regions of (YB-crystallin (N-c-T) resulted in multimeric complexes, but did not restore chaperonelike activity. Replacing the tail region of Hsp12.2 with that of alphaB-crystallin (n-c-T) did not alter the tetrameric structure and lack of chaperone activity. Similarly, providing (alphaB-crystallin with the tail of Hsp12.2 (N-C-t) did not substantially influence the multimeric complex size, but it reduced the chaperoning ability, especially for small substrates. These results suggest that the conserved alpha -crystallin domain of Hsp12.2 is intrinsically unsuitable to confer chaperonelike activity and confirms that the tail region in alphaB-crystallin modulates chaperonelike capacity in a substrate-dependent manner.

Kokke BPA et al. (1998) FEBS Lett "Caenorhabditis elegans small heat-shock proteins Hsp12.2 and Hsp12.3 form tetramers and have no chaperone-like activity."

de Jong WW, Boelens WC, Leroux MR, Candido EPM, Kokke BPA

[FEBS Lett, 1998]

Four 12.2-12.6 kDa small heat-shock proteins (sHSPs) of Caenorhabditis elegans are the smallest known members of the sHSP family. They essentially comprise the characteristic C-terminal 'alpha-crystallin domain' of the sHSPs, having a very short N-terminal region, and lacking a C-terminal tail. Recombinant Hsp12.2 and 12.3 are characterized here. Far-UV CD spectra reveal, as for other sHSPs, predominantly a beta-sheet structure. By gel permeation and crosslinking, they are the first sHSPs shown to occur as tetramers, rather than forming the usual large multimeric complexes. Exceptionally, too, both appear devoid of in vitro chaperone-like abilities. This supports the notion that tetramers are the building blocks of sHSP complexes, and that higher multimer formation, mediated through the N-terminal domains, is a prerequisite for chaperone-like activity.