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Degradation of MinD oscillator complexes by Escherichia coli ClpXP
Christopher J LaBreck1, Catherine E Trebino1, Colby N Ferreira1
1Department of Cell & Molecular Biology, The University of Rhode Island, Kingston, Rhode Island, USA.
Abstract:
MinD is a cell division ATPase in Escherichia coli that oscillates from pole to pole and regulates the spatial position of the cell division machinery. Together with MinC and MinE, the Min system restricts assembly of the FtsZ-ring to midcell, oscillating between the opposite ends of the cell and preventing FtsZ-ring misassembly at the poles. Here, we show that the ATP-dependent bacterial proteasome complex ClpXP degrades MinD in reconstituted degradation reactions in vitro and in vivo through direct recognition of the MinD N-terminal region. MinD degradation is enhanced during stationary phase, suggesting that ClpXP regulates levels of MinD in cells that are not actively dividing. ClpXP is a major regulator of growth phase-dependent proteins, and these results suggest that MinD levels are also controlled during stationary phase. In vitro, MinC and MinD are known to coassemble into linear polymers; therefore, we monitored copolymers assembled in vitro after incubation with ClpXP and observed that ClpXP promotes rapid MinCD copolymer destabilization and direct MinD degradation by ClpXP. The N terminus of MinD, including residue Arg 3, which is near the ATP-binding site in sequence, is critical for degradation by ClpXP. Together, these results demonstrate that ClpXP degradation modifies conformational assemblies of MinD in vitro and depresses Min function in vivo during periods of reduced proliferation.
Insights
The bacterial proteasome complex ClpXP degrades MinD, a key cell division protein, directly targeting its N-terminal region. This degradation is enhanced in stationary phase, regulating MinD levels when cells are not actively dividing.
Area of Science:
- Bacterial cell division
- Protein degradation
- Escherichia coli biology
Background:
- MinD is an ATPase essential for bacterial cell division in Escherichia coli.
- The Min system (MinC, MinD, MinE) ensures proper FtsZ-ring assembly at midcell, preventing polar misassembly.
- MinD oscillates pole-to-pole, regulating the cell division machinery's spatial position.
Purpose of the Study:
- To investigate the role of the ATP-dependent bacterial proteasome complex ClpXP in MinD regulation.
- To determine if ClpXP degrades MinD and identify the mechanism of degradation.
- To understand how ClpXP influences MinD levels during different growth phases.
Main Methods:
- In vitro degradation assays using reconstituted proteasome and MinD.
- In vivo studies in Escherichia coli to observe MinD degradation.
- Analysis of MinD N-terminal region importance for degradation.
- Monitoring MinCD copolymer stability and degradation after ClpXP incubation.
Main Results:
- ClpXP directly degrades MinD in vitro and in vivo by recognizing its N-terminal region.
- MinD degradation by ClpXP is enhanced during the stationary phase.
- ClpXP destabilizes MinCD copolymers and degrades MinD within them.
- Residue Arg 3 in the MinD N terminus is critical for ClpXP-mediated degradation.
Conclusions:
- ClpXP acts as a protease that degrades MinD, thereby modulating its function.
- ClpXP regulates MinD levels, particularly during stationary phase when cell division is reduced.
- This degradation pathway impacts MinD's role in spatial regulation of cell division machinery during non-proliferative states.
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