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bioRxiv · 10.1101/2023.08.31.555675

Structural basis of aggregate binding by the AAA+ disaggregase ClpG

Katikaridis, P.·Simon, B.·Jenne, T.·Moon, S.·Lee, C.·Hennig, J.·Mogk, A.
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Abstract

Severe heat stress causes massive loss of essential proteins by aggregation necessitating a cellular activity that rescues aggregated proteins. This activity is executed by ATP-dependent, ring-forming, hexameric AAA+ disaggregases. Little is known about the recognition principles of stress-induced protein aggregates. How can disaggregases specifically target aggregated proteins while avoiding binding to soluble non-native proteins? Here, we determined by NMR spectroscopy the core structure of the aggregate targeting N1 domain of the bacterial AAA+ disaggregase ClpG, which confers extreme heat resistance to bacteria. N1 harbors a Zn2+-coordination site that is crucial for structural integrity and disaggregase functionality. Conserved hydrophobic N1 residues located on a {beta}-strand were found crucial for aggregate targeting and disaggregation activity. Mixing experiments with N1-truncated AAA+ hexamers revealed that a minimal number of four N1 domains must be present in a AAA+ ring for high disaggregation activity. We suggest that multiple N1 domains increase substrate affinity through avidity effects. These findings define the recognition principle of a protein aggregate by a disaggregase, involving simultaneous contacts with multiple hydrophobic substrate patches located in close vicinity on an aggregate surface. This binding mode ensures selectivity for aggregated proteins while sparing soluble, non-native protein structures from disaggregase activity.

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Katikaridis, P., Simon, B., Jenne, T., Moon, S., Lee, C., Hennig, J., Mogk, A.. 2023-08-31. Structural basis of aggregate binding by the AAA+ disaggregase ClpG. https://doi.org/10.1101/2023.08.31.555675

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