FtsZ from Divergent Foreign Bacteria Can Function for Cell Division inEscherichia coli

Abstract

FtsZs from Mycoplasma pulmonis (MpuFtsZ) and Bacillus subtilis (BsFtsZ) are only 46% and 53% identical in amino acid sequence to FtsZ from Escherichia coli (EcFtsZ). In the present study we show that MpuFtsZ and BsFtsZ can function for cell division in E. coli provided we make two modifications. First, we replaced their C-terminal tails with that from E. coli, giving the foreign FtsZ the binding site for E. coli FtsA and ZipA. Second, we selected for mutations in the E. coli genome that facilitated division by the foreign FtsZs. These suppressor strains arose at a relatively high frequency of 10 ؊3 to 10 ؊5 , suggesting that they involve loss-offunction mutations in multigene pathways. These pathways may be negative regulators of FtsZ or structural pathways that facilitate division by slightly defective FtsZ. Related suppressor strains were obtained for EcFtsZ containing certain point mutations or insertions of yellow fluorescent protein. The ability of highly divergent FtsZs to function for division in E. coli is consistent with a two-part mechanism. FtsZ assembles the Z ring, and perhaps generates the constriction force, through self interactions; the downstream division proteins remodel the peptidoglycan wall by interacting with each other and the wall. The C-terminal peptide of FtsZ, which binds FtsA, provides the link between FtsZ assembly and peptidoglycan remodeling.FtsZ assembles into the Z ring at the center of the bacterial cell, and this ring eventually constricts as the cell divides. There is much evidence that the Z ring provides the force for constriction, and although not definitively proven (an alternative for cells with a cell wall is that invagination of the cell wall generates the constriction force), we will assume that this is the case. Other proteins associate with the Z ring and are essential for the eventual constriction of the Z ring. FtsZ is required for the association of all other division proteins. In Escherichia coli, Z-ring assembly requires either FtsA or ZipA, which serve to tether FtsZ to the membrane (39, 40). FtsK is the next protein to associate with the Z ring, and it requires FtsA and perhaps ZipA (17,40). In E. coli the downstream division proteins assemble in a mostly linear fashion (4, 5). However, recent work suggests that the pathway is not strictly linear and involves cooperative binding of some downstream proteins to two or more partners (18-20, 27, 47). For more detailed discussion of Z-ring assembly and bacterial cell division, see recent reviews (15,19,32,44,51).Several proteins are known to bind directly to FtsZ. FtsA and ZipA both bind the same site: a 15-to 17-amino-acid peptide at the very C terminus of FtsZ (23, 31, 49, 52). In Mycobacterium tuberculosis, which has no FtsA or ZipA, this peptide binds FtsW (9), and this binding may occur in other species. MinC binds FtsZ (26), probably on the bottom protofilament interface of FtsZ. MinC is not essential for the assembly and constriction of Z rings, but in its absence extra Z rings assemble near the cell ends, ...

Extreme C Terminus of Bacterial Cytoskeletal Protein FtsZ Plays Fundamental Role in Assembly Independent of Modulatory Proteins

“…55). Intriguingly, in their study, Osawa and Erickson (55) were able to obtain second site suppressor mutations in the E. coli chromosome that permitted growth of E. coli cells expressing the B. subtilis chimera protein as its only source of FtsZ. Coupled with the localization data, this finding would support the view that an unidentified FtsZ-interacting protein may titrate ectopic FtsZ away from the site of division.…”

“…5A in Ref. 55). Intriguingly, in their study, Osawa and Erickson (55) were able to obtain second site suppressor mutations in the E. coli chromosome that permitted growth of E. coli cells expressing the B. subtilis chimera protein as its only source of FtsZ.…”

Evolution of the cytoskeleton

“…As FtsZ later evolved in the diverging species, it preserved this mechanism largely unchanged. (In this regard, it is noteworthy that FtsZ from B. subtilis and M. pulmonis can function for division in E. coli (52)). Apparently this core 45−55% sequence identity is sufficient to preserve the features needed for the cell division mechanism.…”

FtsZ in Bacterial Cytokinesis: Cytoskeleton and Force Generator All in One

“…one-third of that of the wild-type FtsZ, it labels the Z ring without introducing obvious defects in division. Our lab has recently derived an E. coli strain that can use FtsZ-YFP as the sole source of FtsZ (138). This strain has a second-site mutation, whose nature is not known, somewhere in the genome.…”