Cellular localization of a Hsp90 homologue in Porphyromonas gingivalis

We previously reported an association between elevated serum antibody titer s to the 90-kDa human heat shock protein (Hsp90), periodontal health and co lonization by Porphyromonas gingivalis. In this study, we examined the cell ular localization of the Hsp90 homologue of P. gingivalis. Cultures of P. g ingivalis were heat-stressed (45 degrees C) and examined for localization o f the Hsp90 homologue. Heat stress induced a 4-5-fold increase in anti-Hsp9 0 antibody reactivity over that of the unstressed controls. Western blot an alysis revealed two bands (44 and 68 kDa) that reacted with anti-Hsp90 anti bodies. The 68-kDa band was heat-inducible, while the 44-kDa band was not. Immunogold staining revealed that the Hsp90 homologue localized principally to the membrane and extracellular vesicles. Subcellular fractionation conf irmed that the Hsp90 homologue was primarily membrane-associated. (C) 1999 Federation of European Microbiological Societies. Published by Elsevier Sci ence B.V. All rights reserved.