The In Vitro Non-Tetramerizing ZapAI83E Mutant Is Unable to Recruit ZapB to the Division Plane In Vivo in Escherichia coli.

Nils Y Meiresonne,Tanneke Den Blaauwen

doi:10.3390/ijms21093130

Nils Y Meiresonne, Tanneke Den Blaauwen

Open Access

https://doi.org/10.3390/ijms21093130

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Abstract

Bacterial cell division is guided by filamenting temperature-sensitive Z (FtsZ) treadmilling at midcell. FtsZ itself is regulated by FtsZ-associated proteins (Zaps) that couple it to different cellular processes. Z-associated protein A (ZapA) is known to enhance FtsZ bundling but also forms a synchronizing link with chromosome segregation through Z-associated protein B (ZapB) and matS-bound MatP. ZapA likely exists as dimers and tetramers in the cell. Using a ZapA mutant that is only able to form dimers in vitro (ZapAI83E), this paper investigates the effects of ZapA multimerization state on its interaction partners and cell division. By employing fluorescence microscopy and Förster resonance energy transfer in vivo it was shown that ZapAI83E is unable to complement a zapA deletion strain and localizes diffusely through the cell but still interacts with FtsZ that is not part of the cell division machinery. The diffusely-localized ZapAI83E is unable to recruit ZapB, which in its presence localizes unipolarly. Interestingly, the localization profiles of the chromosome and unipolar ZapB anticorrelate. The work presented here confirms previously reported in vitro effects of ZapA multimerization in vivo and places it in a broader context by revealing the strong implications for ZapB and chromosome localization and ter linkage.

Highlights

The cell division protein Z-associated protein A (ZapA) is broadly conserved among Gram-negative and -positive bacteria [1,2]
ZapA is an filamenting temperature-sensitive Z (FtsZ)-associated protein involved in stabilization of the proto-ring and synchronizing bacterial cell division with chromosome segregation through ter linkage
ZapA can exist as tetramers or dimers and in vitro evidence suggests its functionality relies on its tetrameric form, even though the dimer can still bind to FtsZ [5,6]

Summary

Introduction

The cell division protein Z-associated protein A (ZapA) is broadly conserved among Gram-negative and -positive bacteria [1,2]. Many of the ZapA-enhanced FtsZ polymerization studies were performed in vitro at non-physiological conditions that themselves promote FtsZ filamentation and bundling [2]. Experiments performed under physiological conditions revealed a more dynamic stabilizing effect of ZapA on FtsZ bundle formation [3]. In vitro work showed that transient interactions of ZapA with FtsZ increase the spatial order and stabilize the architecture of the FtsZ filament network without affecting its treadmilling velocity [5]. These effects were only observed for ZapA that was able to interact with FtsZ [5].

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