ATP-binding site lesions in FtsE impair cell division

Area of Science:

• Bacterial cell division mechanisms
• Molecular machinery of Escherichia coli
• Protein complex function in prokaryotes

Background:

• FtsE and FtsX form a complex in Escherichia coli, localized to the septal ring.
• Absence of FtsEX impairs cell division and septal ring protein recruitment.
• Previous hypotheses suggested FtsEX facilitates membrane protein insertion.

Purpose of the Study:

• To investigate the precise role of the FtsEX complex in Escherichia coli cell division.
• To determine if FtsEX functions as a membrane protein transporter.
• To elucidate the mechanism by which FtsEX influences septal ring assembly and function.

Main Methods:

• Depletion studies to assess protein levels in membrane fractions.
• Localization studies using FtsX in FtsE-deficient cells.
• Analysis of mutant FtsE proteins with impaired ATP-binding.
• Topology analysis of the FtsX protein.

Main Results:

• FtsEX-depleted cells retain normal membrane levels of key division proteins (FtsK, FtsQ, FtsI, FtsN).
• FtsX localizes to septal rings independently of FtsE, indicating FtsX targets the complex.
• ATP-binding-deficient FtsE mutants support ring assembly but not constriction.
• FtsX topology is inconsistent with a substrate-specific channel.

Conclusions:

• FtsEX likely utilizes ATP to promote cell division constriction, not membrane protein insertion.
• The FtsEX complex may not function as a traditional transporter despite ATP hydrolysis.
• FtsEX is essential for recruiting other division proteins to the septal ring for proper function.