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Updated: Mar 22, 2026

Measuring In Vitro ATPase Activity for Enzymatic Characterization
Published on: August 23, 2016
p97 Composition Changes Caused by Allosteric Inhibition Are Suppressed by an On-Target Mechanism that Increases the
Nam-Gu Her1, Julia I Toth1, Chen-Ting Ma2
1Tumor Initiation and Maintenance Program, NCI-Designated Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA.
Abstract:
The AAA ATPase p97/VCP regulates protein homeostasis using a diverse repertoire of cofactors to fulfill its biological functions. Here we use the allosteric p97 inhibitor NMS-873 to analyze its effects on enzyme composition and the ability of cells to adapt to its cytotoxicity. We found that p97 inhibition changes steady state cofactor-p97 composition, leading to the enrichment of a subset of its cofactors and polyubiquitin bound to p97. We isolated cells specifically insensitive to NMS-873 and identified a new mutation (A530T) in p97. A530T is sufficient to overcome the cytotoxicity of NMS-873 and alleviates p97 composition changes caused by the molecule but not other p97 inhibitors. This mutation does not affect NMS-873 binding but increases p97 catalytic efficiency through altered ATP and ADP binding. Collectively, these findings identify cofactor-p97 interactions sensitive to p97 inhibition and reveal a new on-target mechanism to suppress the cytotoxicity of NMS-873.
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