A gradient‐forming MipZ protein mediating the control of cell division in the magnetotactic bacterium Magnetospirillum gryphiswaldense

Abstract

Cell division needs to be tightly regulated and closely coordinated with other cellular processes to ensure the generation of fully viable offspring. Here, we investigate division site placement by the cell division regulator MipZ in the alphaproteobacterium Magnetospirillum gryphiswaldense, a species that forms linear chains of magnetosomes to navigate within the geomagnetic field. We show that M. gryphiswaldense contains two MipZ homologs, termed MipZ1 and MipZ2. MipZ2 localizes to the division site, but its absence does not cause any obvious phenotype. MipZ1, by contrast, forms a dynamic bipolar gradient, and its deletion or overproduction cause cell filamentation, suggesting an important role in cell division. The monomeric form of MipZ1 interacts with the chromosome partitioning protein ParB, whereas its ATP-dependent dimeric form shows non-specific DNA-binding activity. Notably, both the dimeric and, to a lesser extent, the monomeric form inhibit FtsZ polymerization in vitro. MipZ1 thus represents a canonical gradient-forming MipZ homolog that critically contributes to the spatiotemporal control of FtsZ ring formation. Collectively, our findings add to the view that the regulatory role of MipZ proteins in cell division is conserved among many alphaproteobacteria. However, their number and biochemical properties may have adapted to the specific needs of the host organism.

Bacterial cell division at a glance

“…In most well-studied organisms, spatial regulation of Z-ring assembly is primarily mediated by negative regulators of FtsZ polymerization. The Min proteins function in Escherichia coli (de Boer et al, 1989) and Bacillus subtilis (Levin et al, 1992) to inhibit FtsZ polymerization near the cell poles, and a functionally analogous protein called MipZ fulfills a similar function in α-proteobacteria (Thanbichler and Shapiro, 2006;Toro-Nahuelpan et al, 2019), with the ultimate result being the accurate placement of the Z-ring at the midcell. Additional negative (e.g.…”

Rules and Exceptions: The Role of Chromosomal ParB in DNA Segregation and Other Cellular Processes

“…Finally, a functional analysis of two MipZ-like proteins encoded by mipZ1 and mipZ2 in Magnetospirillum gryphiswaldense revealed that MipZ1 is crucial for proper cell division, and MipZ2 has only a minor effect on this process [184]. MipZ1 interacts with ParB and forms a bipolar comet-like gradient akin to MipZ of C. crescentus, while MipZ2 localizes to the cell division site similar to the MipZ of R. sphaeroides [184].…”

The CTPase activity of ParB determines the size and dynamics of prokaryotic DNA partition complexes

“…The segregation process is thought to be driven by a ratchet-like mechanism, in which ParB follows a retracting polarized gradient of nucleoid-associated ParA molecules (Fogel and Waldor, 2006;Lim et al, 2014;Vecchiarelli et al, 2014;reviewed by Jalal and Le [2020]). In addition to its role in origin segregation, the partition complex can have several additional functions (Kawalek et al, 2020), including the polar attachment of the origin regions (Bowman et al, 2008;Donovan et al, 2012;Ebersbach et al, 2008;Yamaichi et al, 2012), the loading of bacterial condensin complexes (Bo ¨hm et al, 2020;Gruber and Errington, 2009;Sullivan et al, 2009;Tran et al, 2017), and the regulation of division site placement (Thanbichler and Shapiro, 2006;Toro-Nahuelpan et al, 2019).…”