Role of the Carboxy Terminus of Escherichia coli FtsA in Self-Interaction and Cell Division

Abstract

The role of the carboxy terminus of the Escherichia coli cell division protein FtsA in bacterial division has been studied by making a series of short sequential deletions spanning from residue 394 to 420. Deletions as short as 5 residues destroy the biological function of the protein. Residue W415 is essential for the localization of the protein into septal rings. Overexpression of the ftsA alleles harboring these deletions caused a coiled cell phenotype previously described for another carboxy-terminal mutation (Gayda et al., J. Bacteriol. 174:5362-5370, 1992), suggesting that an interaction of FtsA with itself might play a role in its function. The existence of such an interaction was demonstrated using the yeast two-hybrid system and a protein overlay assay. Even these short deletions are sufficient for impairing the interaction of the truncated FtsA forms with the wild-type protein in the yeast two-hybrid system. The existence of additional interactions between FtsA molecules, involving other domains, can be postulated from the interaction properties shown by the FtsA deletion mutant forms, because although unable to interact with the wild-type and with FtsA⌬1, they can interact with themselves and cross-interact with each other. The secondary structures of an extensive deletion, FtsA⌬27, and the wild-type protein are indistinguishable when analyzed by Fourier transform infrared spectroscopy, and moreover, FtsA⌬27 retains the ability to bind ATP. These results indicate that deletion of the carboxy-terminal 27 residues does not alter substantially the structure of the protein and suggest that the loss of biological function of the carboxy-terminal deletion mutants might be related to the modification of their interacting properties.FtsA is an essential cell division protein of Escherichia coli that is widely conserved in bacteria. Together with ftsZ, which codes for a GTPase analog of the eukaryotic tubulin, ftsA forms one of the most frequently conserved gene pairs among the cell division genes in the eubacteria. Based on sequence homology it has been proposed that FtsA belongs to the sugar kinase/hsp70/actin superfamily (4). This superfamily comprises several proteins with a common two-domain topology and the ability to bind and hydrolyze ATP. FtsA binds to columns of ATP-agarose and can be isolated from cells either as a phosphorylated or a nonphosphorylated form (29), but so far no other biochemical function has been described for this protein.FtsA is present both in the cytoplasm and in the cytoplasmic membrane (29), where it forms a structural part of the septum (32). It has been proposed that FtsA is a component of a membrane-associated complex (septator or divisome), which would include periplasmic, transmembrane, and cytoplasmic proteins acting coordinately to perform septation (27,35). Genetic analysis suggests that FtsA may interact, directly or indirectly, with other cell division proteins, such as FtsZ, PBP3, FtsQ, and FtsN (9,10,24,33,34). The FtsZ/FtsA ratio is important for cell division, an...

Interaction Network amongEscherichia coliMembrane Proteins Involved in Cell Division as Revealed by Bacterial Two-Hybrid Analysis

“…FtsZ is able to polymerize to form a ring at the cell center (3,38), and the C-terminal cytosolic domain of FtsZ has been shown to associate with ZipA and FtsA (24,26,32,34,44). Moreover, FtsA is able to dimerize (9,46). Characterization of the interactions involving the other Fts proteins has been limited, probably because these proteins are membrane bound and some of them are expressed at very low levels.…”

Assembly Dynamics of the Bacterial Cell Division Protein FtsZ: Poised at the Edge of Stability

“…The phosphorylation state of FtsA appears to correlate with ATP binding and membrane association, but a mutation that prevents phosphorylation and in vitro ATP binding still rescues conditional ftsA alleles (122). FtsA is part of the actin/hexokinase/HSP70 superfamily (139) and has been shown to dimerize (34,152), but to date there is no evidence that it polymerizes. MreB, a protein required for maintaining cell shape, is a better candidate for a functional prokaryotic homolog of actin (54,138).…”

In the Beginning, Escherichia coli Assembled the Proto-ring: An Initial Phase of Division

“…In consequence, a role as a central hub to integrate signals that modulate divisome assembly in E. coli has been assigned to this C-terminal end of FtsZ (53). In (56,57). The ATPase activity of FtsA has not been firmly established, perhaps because its hydrolytic activity is low and an unidentified cofactor is required in vivo for its full activation.…”

“…In (55). The self-interaction of FtsA is essential for the E. coli division process (56,57). The ATPase activity of FtsA has not been firmly established, perhaps because its hydrolytic activity is low and an unidentified cofactor is required in vivo for its full activation.…”

“…When attached to a lipid monolayer, FtsA protofilaments from Thermotoga maritima (60) and E. coli (61) undergo a conformational change, forming straight tubular structures. A short C-terminal amphipathic helix in FtsA is responsible for its attachment to the membrane (6), and it also diminishes selfinteraction (56).…”