The bacterial cytoplasm is an openly diffusive compartment that contains more than two million proteins. Surprisingly, the cytoplasm is not a chaotic mixture, but instead highly organized by the formation of complex macromolecular assemblies comprised of groups of proteins. Cell poles are prominent examples of macromolecular assembly sites, and proteins that assemble at these locations control chromosome replication and segregation, cell-cycle dependent gene expression, motility, and biofilm formation. The Polar Organizing Protein Z (PopZ), forms polymeric scaffolds at both cell poles in Caulobacter crescentus, and is required for recruiting regulatory proteins from the cytoplasm. We have previously shown that the PopZ scaffold interacts directly with at least eight different target proteins. In the current study, we have utilized solution nuclear magnetic resonance (NMR) spectroscopy to investigate the interaction of PopZ with its binding partners and to structurally characterize a truncated version of PopZ that stays monomeric and soluble in solution, yet it is fully capable of binding the target proteins. While PopZ primarily adopts an intrinsically disordered conformation, there is a short alpha-helical segment close the N-terminus which participates in protein binding. These results contribute to our understanding of bacterial hub proteins and to developing a more generalized mechanism for the organization of complex bacterial networks.

Structural characterization and binding studies of polar organizing protein Z from Caulobacter crescentus using NMR spectroscopy

2019 Fall National Meeting

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