Peptide Linkers within the Essential FtsZ Membrane Tethers ZipA and FtsA Are Nonessential for Cell Division

Abstract

Bacteria such as Escherichia coli divide by organizing filaments of FtsZ, a tubulin homolog that assembles into dynamic treadmilling membrane-associated protein filaments at the cell midpoint. FtsA and ZipA proteins are required to tether these filaments to the inner face of the cytoplasmic membrane, and loss of either tether is lethal. ZipA from E. coli and other closely related species harbors a long linker region that connects the essential N-terminal transmembrane domain to the C-terminal globular FtsZ-binding domain, and part of this linker includes a P/Q-rich peptide that is predicted to be intrinsically disordered. We found unexpectedly that several large deletions of the ZipA linker region, including the entire P/Q rich peptide, had no effect on cell division under normal conditions. However, we found that the loss of the P/Q region made cells more resistant to excess levels of FtsA and more sensitive to conditions that displaced FtsA from FtsZ. FtsA also harbors a short ∼20-residue peptide linker that connects the main globular domain with the C-terminal amphipathic helix that is important for membrane binding. In analogy with ZipA, deletion of 11 of the central residues in the FtsA linker had little effect on FtsA function in cell division. IMPORTANCE Escherichia coli cells divide using a cytokinetic ring composed of polymers of the tubulin-like FtsZ. To function properly, these polymers must attach to the inner surface of the cytoplasmic membrane via two essential membrane-associated tethers, FtsA and ZipA. Both FtsA and ZipA contain peptide linkers that connect their membrane-binding domains with their FtsZ-binding domains. Although they are presumed to be crucial for cell division activity, the importance of these linkers has not yet been rigorously tested. Here, we show that large segments of these linkers can be removed with few consequences for cell division, although several subtle defects were uncovered. Our results suggest that ZipA, in particular, can function in cell division without an extended linker.

Anchors: A way for FtsZ filaments to stay membrane bound

“…This helix is conserved in FtsAs from a wide variety of species (Pichoff & Lutkenhaus, 2005) and is connected to the core polymerizing domain of FtsA through an intrinsically disordered linker (IDL) (Figures 1 and 2). E. coli FtsA has a short (~25 residues) IDL that can withstand some amino acid substitutions but cannot be removed (Schoenemann et al, 2020). Most other FtsAs have similarly short IDLs, but several Gram‐positive species including Streptococcus pneumoniae and Deinococcus radiodurans contain FtsA orthologs with considerably longer IDL domains (>100 additional linker residues in the case of D. radiodurans ).…”

“…Membrane topology and domain organization of FtsZ membrane tethers. Linear domains of Escherichia coli FtsA and ZipA (Hale et al, 2000; Schoenemann et al, 2020), Bacillus subtilis SepF (Duman et al, 2013) and B. subtilis EzrA (Cleverley et al, 2014; Haeusser et al, 2007) are depicted along with relevant residue numbers that demarcate the domains. Known crystal structures for ZipA, SepF, and EzrA are shown to the right of each linear domain diagram along with their Protein Data Bank (pdb) accession numbers.…”