Characterization of Chloroplast Hsp90 Homologue

Members of the 90-kDa heat shock protein (HSP90) family regulate diverse cellular processes acting as molecular chaperones from prokaryotes to eukaryotes interacting with various proteins, cochaperones and other chaperones. As there is little information available about the functions of organelle Hsp90s in higher plants, this research was designed to characterize chloroplast-targeted Arabidopsis homologues of Hsp90 (AtHsp90). We identified the respective Arabidopsis homologue from the Arabidopsis thaliana databases, which had the higher plastid localizing probability by in silico analysis. C-terminally modified precursor type of AtHsp90 was successfully imported in vitro into pea chloroplasts. The processed, mature AtHsp90 was recovered in the soluble stroma extracts after post-import protease treatments, confirming its localization at the stroma. Possible functions of stromal Hsp90s are discussed.