Visualizing Chaperone-mediated Multistep Assembly of the Human 20S Proteasome

Overview

Journal bioRxiv

Date 2024 Feb 8

PMID 38328185

Authors

Frank Adolf

Jiale Du

Ellen A Goodall

Richard M Walsh Jr

Shaun Rawson

Susanne von Gronau

J Wade Harper

John Hanna

Brenda A Schulman

Affiliations

Soon will be listed here.

Abstract

Dedicated assembly factors orchestrate stepwise production of many molecular machines, including the 28-subunit proteasome core particle (CP) that mediates protein degradation. Here, we report cryo-EM reconstructions of seven recombinant human subcomplexes that visualize all five chaperones and the three active site propeptides across a wide swath of the assembly pathway. Comparison of these chaperone-bound intermediates and a matching mature CP reveals molecular mechanisms determining the order of successive subunit additions, and how proteasome subcomplexes and assembly factors structurally adapt upon progressive subunit incorporation to stabilize intermediates, facilitate the formation of subsequent intermediates, and ultimately rearrange to coordinate proteolytic activation with gated access to active sites. The structural findings reported here explain many previous biochemical and genetic observations. This work establishes a methodologic approach for structural analysis of multiprotein complex assembly intermediates, illuminates specific functions of assembly factors, and reveals conceptual principles underlying human proteasome biogenesis.

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