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The ParC/ParP system in the localization and segregation of chemotaxis signalling arrays in Vibrio cholerae and Vibrio parahaemolyticus

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Alvarado Rodriguez,  Alejandra Guadalupe
Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Max Planck Society;

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Alvarado Rodriguez, A. G. (2018). The ParC/ParP system in the localization and segregation of chemotaxis signalling arrays in Vibrio cholerae and Vibrio parahaemolyticus. PhD Thesis, Philipps-University Marburg, Marburg.


Cite as: http://hdl.handle.net/21.11116/0000-0004-4670-F
Abstract
Chemotaxis proteins organize into large, highly ordered arrays. Particularly, in the enteric bacteria Vibrio cholerae and Vibrio parahaemolyticus, chemotaxis arrays are found at the cell pole, and their distribution follows a cell cycle dependent localization. The ParC/ParP system mediates this localization pattern and without either ParC or ParP, arrays are no longer positioned at the cell poles and fail to segregate upon division. Localization of arrays in these bacteria follow a hierarchical process, where arrays are tethered by ParP, which in turn links them to ParC, an ATPase that serves as a cell pole determinant in Vibrios. Here, we analyze the mechanism behind ParP’s ability to access the chemotaxis arrays and positions them at the cell pole. Furthermore, we show that even in the absence of histidine kinase CheA proteins, the arrays still exhibit the native spatial localization and the iconic hexagonal packing of the receptors. We show that the V. cholerae Cluster II array is versatile in respect of array composition for auxiliary chemotaxis proteins, such as ParP and that these arrays are structurally less stable due to their lower CheA occupancy in comparison to the ultrastable arrays found in E.coli. Additionally, we examine the dynamic localization of ParC and evaluate its influence in the overall localization of the arrays and ParP. We show that ParP’s C-terminus integrates into the core unit of signaling arrays through interactions with MCP proteins and the histidine kinase CheA. Our results indicate that ParP’s intercalation within the core units facilitates array formation, whereas its N-terminal interaction domain enables polar recruitment of arrays and promotes ParP’s own polar localization. Moreover, the data provides evidence that ParP serves as a critical nexus between the formation of the chemotactic arrays and their proper polar recruitment. Additionally, our data revealed that arrays in V. cholerae have the capacity to include several scaffolding proteins, displaying a previously uncharacterized variability. In turn, we demonstrate that this variability explains the high degree of structural instability shown by V. cholerae chemotaxis arrays. Finally, we show that ParC forms a protein gradient in V. parahaemolyticus cells. This protein gradient extends in a decreasing concentration from the cell pole towards mid-cell, and it is essential for ParC’s function in positioning ParP and consequently the chemosensory arrays. Similarly, gradient maintenance requires a continuous cycle of ParC between the cell pole and the cytoplasm, as well as ParC’s ability to associate with DNA and transition into different protein states in a nucleotide dependent manner. The data shows that ParC’s localization dynamics relies upon differential diffusion rates of its distinct protein states. Altogether, this work studies the complexity of the ParC/ ParP system and highlights the importance of each component in the correct placement of the chemotactic signaling arrays.