Chaperones bound, nature

Initial attention in the development of Hsp90 inhibitors as anticancer agents was focused on two natural products, geldanamycin (compound 43, Fig. 8) and radicicol (also called monorden, compound 44, Fig. 8). These compounds bind into the ATP-binding cleft of the N-terminal domain of Hsp90 preventing the chaperone from cycling between its ADP and ATP-bound... 

Landry, S.J., Jordan, R., McMacken, R., and Gierasch, L. M. (1992). Different conformations for the same polypeptide bound to chaperones DnaK and GroEL. Nature (London) 355, 455-457. 

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