The Escherichia coli divisome: born to divide

Abstract

SummarySeptation in Escherichia coli involves complex molecular mechanisms that contribute to the accuracy of bacterial division. The proto-ring, a complex made up by the FtsZ, FtsA and ZipA proteins, forms at the beginning of the process and directs the assembly of the full divisome. Central to this complex is the FtsZ protein, a GTPase able to assemble into a ringlike structure that responds to several modulatory inputs including mechanisms to position the septum at midcell. The connection with the cell wall synthesising machinery stabilizes the constriction of the cytoplasmic membrane. Although a substantial amount of evidence supports this description, many details on how individual divisome elements are structured or how they function are subjected to controversial interpretations. We discuss these discrepancies arising from incomplete data and from technical difficulties imposed by the small size of bacteria. Future work, including more powerful imaging and reconstruction technologies, will help to clarify the missing details on the architecture and function of the bacterial division machinery.

The Soluble Periplasmic Domains of Escherichia coli Cell Division Proteins FtsQ/FtsB/FtsL Form a Trimeric Complex with Submicromolar Affinity

“…The Gram-negative bacterial divisome is a dynamic macromolecular complex formed by at least 10 essential and up to 15 accessory proteins that assemble at the midcell plane to affect cell division through a series of defined steps, including cell constriction, synthesis of the septal wall, and ultimately cell segregation (1,2). Divisome assembly starts with formation of the FtsZ-ring in the cytoplasm and anchoring of the ring in the inner membrane by FtsA and ZipA.…”

“…FtsQ is considered to play a central, yet enigmatic, role in assembly of the divisome through a multitude of transient interactions (1,2). Two-hybrid analyses have suggested that FtsQ interacts with ϳ10 cell division proteins of which the interactions with FtsB and FtsL were confirmed by immunoprecipitation (3).…”

“…Escherichia coli FtsQ is a bitopic membrane protein of 276 residues, including a short cytoplasmic N-terminal domain, a transmembrane (TM) 2 segment, and a large periplasmic domain (4). With respect to biogenesis and routing, FtsQ has been extensively characterized (5,6).…”

Crystal Structure and Site-directed Mutational Analysis Reveals Key Residues Involved in Escherichia coli ZapA Function

“…FtsZ binds and hydrolyzes GTP in vivo (6) and also polymerizes to form the Z-ring at mid-cell. The Z-ring forms prior to cell division and acts as a scaffold for the recruitment of all downstream cell division proteins; together these comprise the "divisome" (7)(8)(9)(10). In Escherichia coli, the divisome includes ϳ20 essential and nonessential proteins (11)(12)(13).…”

“…Included in the divisome are the Zaps (FtsZ-associated proteins): ZapA, ZapB, ZapC, and ZapD (14 -19). These Zaps stabilize the Z-ring by increasing lateral interactions between individual filaments, thus bundling FtsZ to provide a scaffold for divisome assembly (9,20).…”