The assembly of ERs receptors with chaperones and co-chaperones follows a stepwise route. For detailed information check references PMIDs 18451092, 15269596, 20006655. A minimal set includes Dnaja2 (Hsp40), Hspa4 (Hsp70), the essential Hsp90, and the Stip1 (Hop) and Ptges3 (p23) co-chaperones. Other Hsp90 co-chaperones play a role in modulating receptor activity, and they compete for a common chaperone binding site. Of these, Ppid (Cyp40) and Fkbp4 (Fkbp52) appear to be preferred or found in ERs complexes. A characteristic feature of co-chaperones is the presence of a tetratricopeptide repeat (TPR) domain used in chaperone binding. The chaperones and co-chaperones are listed with symbols, aliases in parentheses, full names and links to gene report pages:

Hsp90aa1 (Hsp90, Hsp86, HSP 90-alpha) – heat shock protein 90 alpha family class A member 1
Hsp90ab1 (HSP 90-beta, HSPC2, HSP84) – heat shock protein 90 alpha family class B member 1
Hspa4 (Hsp70) – heat shock protein family A member 4
Dnaja2 (Hsp40) – DnaJ heat shock protein family (Hsp40) member 2 [this is the Idj1 homolog]
Ptges3 (p23) – prostaglandin E synthase 3
Stip1 (Hop) – stress-induced phosphoprotein 1 [co-chaperone]
Ppid (CypD, Cyp40, Cyclophilin D) – peptidylprolyl isomerase D [co-chaperone]
Fkbp4 (Fkbp52) – FK506 binding protein 4 [co-chaperone]