Ding Z, Xu C, Sahu I, Wang Y, Fu Z, Huang M, Wong CCL, Glickman MH, Cong Y

The 26S proteasome is the ATP-dependent protease responsible for regulating the proteome of eukaryotic cells through degradation of mainly ubiquitin-tagged substrates. In order to understand how proteasome responds to ubiquitin signal, we resolved an ensemble of cryo-EM structures of proteasome in the presence of K48-Ub4, with three of them resolved ...

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at near-atomic resolution. We identified a conformation with stabilized ubiquitin receptors and a previously unreported orientation of the lid, assigned as a Ub-accepted state C1-b. We determined another structure C3-b with localized K48-Ub4 to the toroid region of Rpn1, assigned as a substrate-processing state. Our structures indicate that tetraUb induced conformational changes in proteasome could initiate substrate degradation. We also propose a CP gate-opening mechanism involving the propagation of the motion of the lid to the gate through the Rpn6-?2 interaction. Our results enabled us to put forward a model of a functional cycle for proteasomes induced by tetraUb and nucleotide.

Date: Dec. 21, 2018

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