Neighbor-joining distance tree based on Hsp90 sequences indicating that the cytosolic and ER resident forms of these protein form paralogous gene families, which resulted from a gene duplication event very early in the history of eukaryotic cells. Neighbor-joining distance tree based on Hsp90 sequences indicating that the cytosolic and ER resident forms of these protein form paralogous gene families, which resulted from a gene duplication event very early in the history of eukaryotic cells. The bootstrap scores out of 1,000 replicates are shown. Reproduced from reference97 with permission of the publisher. Radhey S. Gupta Microbiol. Mol. Biol. Rev. 1998; doi: