Structural and Functional Analysis of GRP94 in the Closed State Reveals an Essential Role for the Pre-N Domain and a Potential Client-Binding Site

Publication date: 19 September 2017
Source:Cell Reports, Volume 20, Issue 12
Author(s): John D. Huck, Nanette L. Que, Feng Hong, Zihai Li, Daniel T. Gewirth
Hsp90 chaperones undergo ATP-driven conformational changes during the maturation of client proteins, populating a closed state upon ATP binding in which the N-terminal domains of the homodimer form a second inter-protomer dimer interface. A structure of GRP94, the endoplasmic reticulum hsp90, in a closed conformation has not been described, and the determinants that regulate closure are not well understood. Here, we determined the 2.6-Å structure of AMPPNP-bound GRP94 in the closed dimer conformation. The structure includes the pre-N domain, a region preceding the N-terminal domain that is highly conserved in GRP94, but not in other hsp90s. We show that the GRP94 pre-N domain is essential for client maturation, and we identify the pre-N domain as an important regulator of ATPase rates and dimer closure. The structure also reveals a GRP94:polypeptide interaction that partially mimics a client-bound state. The results provide structural insight into the ATP-dependent client maturation process of GRP94.

Graphical abstract

Teaser

Huck et al. determined the structure of the ER hsp90 chaperone GRP94, and they show that it adopts a closed dimer conformation. The non-conserved pre-N-terminal domain is shown to be essential for GRP94 client maturation, but it is structurally distinct. A captured polypeptide fragment in the structure mimics a bound client.


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