Abstract
The peptidoglycan (PG) layer is an intricate and dynamic component of the bacterial cell wall, which requires a constant balance between its synthesis and hydrolysis. FtsEX complex present on the inner membrane is shown to transduce signals to induce PG hydrolysis. FtsE has sequence similarity with the nucleotide-binding domains (NBDs) of ABC transporters. The NBDs in most of the ABC transporters couple ATP hydrolysis to transport molecules inside or outside the cell. Also, this reaction cycle is driven by the dimerization of NBDs. Though extensive studies have been carried out on the Escherchia coli FtsEX complex, it remains elusive regarding how FtsEX complex helps in signal transduction or transportation of molecules. Also, very little is known about the biochemical properties and ATPase activities of FtsE. Because of its strong interaction with the membrane-bound protein FtsX, FtsE stays insoluble upon overexpression in E. coli, and thus, most studies on E. coli FtsE (FtsEEc) in the past have used refolded FtsE. Here in the present paper, for the first time, we report the soluble expression, purification, and biochemical characterization of FtsE from E. coli. The purified soluble FtsE exhibits high thermal stability, exhibits ATPase activity and has more than one ATP-binding site. We have also demonstrated a direct interaction between FtsE and the cytoplasmic loop of FtsX. Together, our findings suggest that during bacterial division, the ATPase cycle of FtsE and its interaction with the FtsX cytoplasmic loop may help to regulate the PG hydrolysis at the mid cell.
Highlights
The bacterial cell division proceeds in two stages
In the FtsEX complex, FtsE forms the nucleotide-binding domain (NBD), and FtsX forms the transmembrane domain (TMD), and both are essential for the bacterial division
The sequence alignment shows the presence of the conserved consensus sequence (Figure 2A) that confirms FtsE as the NBD in the FtsEX complex
Summary
The bacterial cell division proceeds in two stages. In the first stage, chromosome segregation occurs, and in the second stage, the cell identifies the mid-cell position, where the division occurs. The reason for the occurrence of cytokinesis precisely at the mid-cell was unknown until the role of FtsZ in the assembly of the divisome was identified. FtsZ, a tubulin homolog, forms the core skeleton of the divisome by assembling into a ring-like structure at the mid-cell [1,2]. FtsEX, an ABC transporter homolog [3], gets recruited to the Z-ring during the initial stages of the formation of the divisome complex [4,5]. The ABC transporters primarily function as exporters or importers through remarkable conformational changes upon nucleotide-binding and hydrolysis. Apart from their role as a transporter, these family proteins help in the activation of other proteins [6]. FtsEX activates amidases through EnvC, which performs peptidoglycan (PG) hydrolysis
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