Alignment of representative amino acid sequences of the HSP90 family of proteins, showing their conserved/variable regions, functionally important residues, and functional domains. Amino acid residues completely conserved throughout the HSP90 family are shaded in red, and those conserved throughout each subfamily are in green. The regions that distinguish HTPG Groups A, B and C are shaded in yellow. Gaps are marked with"-", the last residue in each line is assigned a number and subfamily names are indicated at the end of each line. The conserved/variable regions are separated by "||" with the names above the alignment, and the cleavage sites located just before the underlined residues. "▼" stands for the functionally important residues experimentally identified: E47 (refers to HSP90AA1) for ATP hydrolysis; D93 for ATP binding ; G95, G132, G135, G137, and G183 for both GA and p23 binding; K112 for GA binding ; R400 and Q404 for ATPase activity; F369 for interdomain interaction ; S231 and S263 for phosphorylation by casein kinase II . The conserved and functional domains are indicated by: "≈" for HSP90 protein family signature; "=" for HSP90 protein; "~" for histidine kinase-like ATPases; "∞" for four-helical cytokine; and "..." for Glutamic acid-rich region. The number of each sequence represents: 1. (HSA)HSP90AA1, 2. (GGA)HSP90AA1, 3. (HSA)HSP90AB1, 4. (GGA)HSP90AB1, 5. (HSA)HSP90B1, 6. (ATH)HSP90B1, 7. (ATH)HSP90C1, 8. (ATH)HSP90C2, 9. (HSA)TRAP1, 10. (DME)TRAP1, 11. (ECO)HTPG1, 12. (BFR)HTPG1.