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. 2020 Mar 2;9(3):587. doi: 10.3390/cells9030587

Figure 1.

Figure 1

Functional cycle of HSP70 chaperones. (A) Structure of HSP70 in low-affinity (ATP) state. ATP binds to NBD, resulting in an open conformation of SBD, ready for client binding [8]. (B) HSP70-HSP40 complex. HSP40 presents non-native clients to HSP70. J-domain of HSP40 binds to HSP70-NBD stimulating its ATPase activity. Binding of HSP70 C-tail to HSP40-CTD1 displaces the client to HSP70, shifting HSP70 to ADP-bound state [16,38,39]. (C) High-affinity (ADP) state. ADP binds to NBD, SBDα forms the lid over SBDβ, locking substrate in SBD [18,28]. (D) HSP70-NEF complex. NEF displaces ADP from NBD, allowing ATP to bind NBD, shifting the HSP70 to low-affinity (ATP) state [8].NBD, nucleotide-binding domain; SBDα/β, substrate-binding domain; NEF, nucleotide exchange factor; CTD1/2, C-terminal peptide-binding domain of HSP40; J; J domain of HSP40.