Characterization of a novel group of basic small heat shock proteins in Xenopus laevis A6 kidney epithelial cells

In this study, we report the detection of a new group of five stress-induci ble basic small heat shock proteins (BShsps) in Xenopus laevis kidney epith elial A6 cells by means of two-dimensional non-equilibrium pH gradient gel electrophoresis. These basic 30-kDa small hsps are distinct from the previo usly described X. laevis acidic hsp30 family on the basis of their charge a nd lack of cross-reactivity with an hsp30 antibody. Furthermore, at least t wo of the five BShsps were present constitutively, an observation that has not been made with the acidic hsp30 family. The heat inducibility of the BS hsps was regulated at the level of transcription as indicated by their inhi bited synthesis in the presence of the transcriptional inhibitor actinomyci n D. Furthermore, the optimal temperature of BShsp induction, temporal patt ern of synthesis, and induction of BShsps by other stressors such as herbim ycin A and sodium arsenite were similar to those reported for the acidic hs p30 family. This study suggests that X. laevis contains at least two unique groups of small heat shock proteins that are coordinately expressed.